2011CHG0076

STUDENTS INDUSTRIAL WORK EXPERIENCE SCHEME (SIWES) WITH STERLING OIL EXPLORATION AND ENERGY PRODUCTION CO. LTD. Supervisor: Prepared by: Mr. Lincoln Bassey Eloka V. Adaeze OUTLINE ABSTRACT DRILLING AND COMPLETIONS 1.1 1.2 1. INTRODUCTION DRILLING 1.2.1 Typical Casing Profile Getting Ready to Spud Spudding Running the Surface Casing Running the Intermediate Casing Running the Production Casing Running the Production Liner 1.2.2 1.2.3 1.2.4 1.2.5 1.2.6 1.2.7 1.3 COMPLETIONS 1.3.1 1.3.2 1.3.3 1.3.4 Single String with Single Packer Dual String with Multiple Packers Single String with Multiple Packers- Selective Zone Christmas (Xmas) Tree 2. PETROLEUM GEOLOGY 2.1 2.2 INTRODUCTION FORMATIONS IN THE NIGER DELTA Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 2 3. MDT PRESSURE GRADIENT SURVEY 3.1 DETERMINATION OF FLUID TYPE AND CONTACTS FROM PRESSURE-DEPTH PLOTS 3.1.1 3.1.2 3.1.3 Introduction Objectives Evaluation 3.1.3.1 OKW-A Reservoir 3.1.3.2 OKW-B Reservoir 3.1.3.3 OKW-C Reservoir 3.1.3.4 E7000 Reservoir 3.1.3.5 E7500 Reservoir 3.1.3.6 E8000 Reservoir 3.1.4 Conclusion 4. PRESSURE VOLUME TEMPERATURE 4.1 PVT ANALYSIS OF FLUID SAMPLES GOTTEN FROM AGU FIELD 4.1.1 4.1.2 4.1.3 4.1.4 Introduction Objectives Results Conclusion 5. APPENDIX Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 3 ABSTRACT Sterling Oil Exploration and Energy Production Co. Ltd (SEEPCO) is an oil company involved in the exploration and production of hydrocarbons in Nigeria. Presently, they operate on two blocks; Okwuibome field located in OML 143, Kwale, Delta State and Agu field located in OPL 277, Owerri, Imo State. During the training period, I was assigned to two different departments; operations department and subsurface department. This report is divided into four sections; drilling and completions, petroleum geology, modular formation dynamics tester (MDT) pressure gradient survey and pressure volume temperature (PVT) analysis, based on my assignments in Sterling. The drilling and completions section contains information about Sterling’s wells, the drilling process applied and the typical casing profile Sterling uses. Also, the type of completions that were used to complete Sterling’s wells along with sketches of the completion strings. The petroleum geology section contains information on the geology of the Niger Delta and the formations in the Niger Delta. The modular formation dynamics tester (MDT) pressure gradient survey involved the use of pressure data to plot graphs which were used to locate the oil, water and/or gas zones along with the location of the oil-water contact and/or gas-oil contacts if any. The pressure volume temperature (PVT) analysis used PVT data gotten from the laboratory to determine the bubble point pressure of the reservoir, formation volume factor, solution gas oil ratio, viscosity and composition of the reservoir fluid. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 4 DRILLING AND COMPLETION Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 5 .1. rate of penetration. assistant driller. making four completions in IV pack sands.1.2 • • • • • DRILLING Drilling contractors Mud contractors Mud loggers Cement contractors Logging company The companies involved in the drilling operations include. Two of the completions were vertical wells while the other two were horizontal wells and they were all shallow sands.1 INTRODUCTION Sterling uses rotary rigs to drill her wells. The logging company performs all well logging operations while drilling. These rigs were operated by BOGEL (the drilling service company). The top drive system was used to drill all Sterling’s wells except OKW-9 where the rotary table system was used. The mud contractors are in charge of mixing mud. The cement contractors are in charge of cementing the casing to the borehole wall. driller. cuttings analyses and so on. the drilling engineer. 1. with input from the Geo-scientist. The mud logger monitors drilling parameters like depth. petrophysicists. Durga-1 and Durga-2. Rotary drilling consists of two types of rotating systems that can be used. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 6 . rotary table system and top drive system. floor men. derrick man. Durga-2 drilled two vertical and one dually completed well. Durga-2 which is used for drilling high pressure and high temperature zones was used to drill these wells because the IV pack sands are deep with high pressure and temperature. tour pusher. reservoir engineers and production engineers decided on the strategy to adopt for the appraisal drilling of proposed wells. Two rotary rigs were assigned. At the planning stages of drilling Sterling’s wells. Durga-1 was used to drill four completions in the II pack sands. The drilling contractors consist of the tool pusher. and derrick pusher. The primary purpose of the cellar is to align the Christmas tree at relative ground level. 1. a well contains multiple intervals of casing successively placed within the previous casing run. The DST tool on the other hand is run in a cased hole section along with the perforating gun. and other equipment. such as 1 ft or 200 ft. Also. The first string of pipe is called the conductor pipe or drive pipe which is usually 30” for Sterling’s wells. The following casing profiles were used for Sterling’s wells design.2 Getting Ready to Spud Drilling land wells begin with digging a cellar which can be from 3-15feet. The pipe is driven into the ground to the point of refusal.2. the inside diameter of the first casing string must be large enough to fit the second bit that will be used to continue drilling. the DST tool measures the formation’s flow pressure.2. • Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 7 . • • • • • Conductor casing Surface casing Intermediate casing Production casing Production liner During drilling of the well(s) the logging tool is run in hole to measure formation parameters.2. allowing room for cement between the outside of the casing and the hole. The MDT takes pressure measurements and pressurized fluid samples. choke. Usually. along with the MDT tool. 1. This allows for easier access to the valves. These fluid samples are taken to the laboratory for PressureVolume-Temperature analysis.1 Typical Casing profile The hole drilled for each casing must be large enough to easily fit the casing inside it.3 • Spudding A large diameter hole is drilled to a specified depth generally relatively shallow. When the gun perforates the casing.1. Below are the steps taken preparatory to drilling and completion of wells. Running the Production Liner The production liner is run to the total depth of the well. the 4 ½” production liner is installed and cemented in place.5 • Running the Intermediate Casing After the 17 ½” hole has been drilled.1. 1. 1.2.2.6 • Running the Production Casing The 12 ¼” hole is drilled and 9-5/8”production casing is run and cemented in place. 1. When the 6” hole is drilled.2. Cement is circulated to surface of the 20” surface casing.2.7 • See figure below 30” conductor casing cement Casing shoe 26” hole 20” surface casing 17 ½” hole 13 3/8” intermediate casing 12 ¼” hole 9 5/8” production casing 6” hole 4 ½” production liner Figure: typical casing profile Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 8 . 13-3/8” intermediate casing casing is run in the hole and cemented to a predetermined depth to ensure a good cement bond is obtained between the surface casing and the intermediate casing.4 • Running the Surface Casing After drilling 26” surface hole. and oil or gas zones within that depth range of the formation. the 20” surface casing is run to a specified depth to isolate any fresh water. salt water. such as carbonate reservoirs.Selective Zone Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 9 . Wells can be completed as. The tubing configurations used includes the following. thereby opening and connecting the reservoir to the wellbore. tools and equipments placed in a wellbore to convey. • Single string with single packer • Dual string with multiple packers • Single string with multiple packers. single selective completions etc  Naturally flowing or artificially flowing wells Openhole completions are feasible only in reservoirs with sufficient formation strength to prevent caving or sloughing. pump or control the production or injection of fluids. dual string completions. Cased hole completions are feasible in reservoirs without sufficient formation strength such as sandstone reservoirs which are unconsolidated.1.3 COMPLETIONS Well completion is composed of tubular. Cased hole involve using a set of casing set through the producing reservoir and cemented in place.  Open hole or cased hole  Single string completions. Fluid flow is established by perforating the casing and cement sheath. Sterling does cased hole completions because formation structure in the Niger delta is sand stone. 1. The packer holds the tubing string in place and establishes hydraulic separation between the tubing string and the casing or liner. installed in place and pressure tested. There is both tubing and annulus flow. The packer is run in hole. Flow Cou pling Selective Lan din g Nipple Tubin g Seal Divider Sliding Sleeve Packer No-Go Nipple Figure: single string with single packer Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 10 .1 Single String with Single Packer This is a single string flow conduit. and then the tubing string is run inbetween the packer.3. 1. In the figure below.2 Dual String with Multiple Packers In the dual string with multiple packers. the fluids in the upper zone is produced through the short string which is 27/8” OD while the fluids in the lower zone is produced through the long string which is 3-½” OD. The dual string is usually placed in the 9-5/8” production casing.3. several zones can be lifted simultaneously. Sliding Sleeve No-Go Nipple Packer Flow Coupling Selective Landing Nipple Blast Joint Polished Nipple Tubing Seal Divider Packer No-Go Nipple Figure: dual string with multiple packers Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 11 . Sliding Sleeve Packer Sliding Sleeve Flow Coupling Selective Landing Nipple Blast Joint Selective Landing Nipple Packer Flow Coupling Blast Joint Selective Landing Nipple Packer No-Go Nipple Figure: single selective string with multiple packers Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 12 . the zones can be produced one at a time or they can be co-mingled depending on government regulations or the quality of the fluids. the producing sections can be opened or closed by shifting the sliding sleeve.3.3 Single String with Multiple Packers. using wireline services.Selective Zone In the single string with multiple packers. If the zones are to be produced one at a time.1. Figure: the production Christmas tree The swab valve provides vertical access to the wellbore. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 13 .4 Christmas (Xmas) Tree At the top of the well completions is the Christmas tree which is an assembly of valves. The surface choke is used to control fluid flow rate or downstream system pressure. see figure above. and a kill wing that may be used for well control or treatment purposes. The two wings featured in the Christmas tree include a production wing connected to the surface production facilities.3. A correctly functioning master valve is so important that two master valves are fitted to the Christmas tree. pressure gauges and choke. Wing valves are incorporated into the wings of a Christmas tree to provide access to the production tubing for production and well control purposes.1. The upper master valve is used on a routine basis. with the lower master valve providing backup in the event that the normal service valve is leaking and needs replacement. directs flow of oil and gas from the well. spools. The tree prevents the release of oil and gas from the well into the environment. including the casing and liner. An important function of the production string is to protect the primary wellbore tubulars. The production string is typically assembled with tubing and completion components in a way that suits the wellbore conditions and the production method. from corrosion and erosion by the reservoir fluid.The production string is the primary conduit through which reservoir fluids are produced to surface. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 14 . 2. PETROLEUM GEOLOGY Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 15 . they are deposited on the previous sediments during which pressure and temperature increases.1 INTRODUCTION Hydrocarbon originates from micro-organisms in the seas. they deposit at the bottom of the sea where they form organic matter as sediments. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 16 . When these organisms die. Some hydrocarbon traps are created by faulting. • Rollover anticline • Listric fault: this is a spoon shaped fault. Some of the faults in the Niger Delta are. As more of these micro-organisms die. Since oil and gas are less dense than water.2. Hydrocarbons are mostly found in anticlinal structures. When rock is folded into an anticline and capped by an overlying impermeable rock. they tend to migrate upward through permeable rock. river. This increase creates a reducing environment during which oxygen is stripped from the sediments and they become compacted thereby forming sedimentary rocks. they are sought out by geologists who explore for oil and gas. then oil and gas will migrate up the slope of the fold to the crest and accumulate there. as a result. lakes and land. In this formation. there is sand and shale intercalation and the water in Agbada formation is saline resulting in low Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 17 . The Benin formation contains unconsolidated fine beach sand basically.• Collapsed crest: this is where compressional forces push a block of rock upward • Growth fault: this is a situation where the hanging wall is thicker than the footwall • • • 2. Agbada formation is where the hydrocarbon is trapped.2 • • • Counter regional fault: this is a C-shaped fault Antithetic fault: this is a fault where the hanging wall dips to the north Synthetic fault: this is a situation where the hanging wall dips to the south FORMATIONS IN THE NIGER DELTA Benin formation Agbada formation Akata formation There are three formations in the Niger Delta. The gamma ray reading in this formation is low because sand contains little or no radioactive particles. This sand also contains fresh water which has high resistivity and can be mistaken for hydrocarbon. but hydrocarbon can not be found in the benin formation because it is separated from Agbada formation by a very thick shale called the upper agbada shale. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 18 . Therefore if high resistivity is encountered in Agbada.resistivity. it is usually perceived to be hydrocarbon. The Akata formation is where the hydrocarbon is formed before it migrates up to the Agbada formation. This formation consists mainly of marine shales and the pressure and temperature here is very high because of its position. 3. MDT PRESSURE GRADIENT SURVEY Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 19 . The reservoir quality of the IID sands is good with a porosity ranging from 26 to 28%. IVA-1 reservoir has 49° API gravity with Gas Oil Ratio (GOR) of about 2000scf/bbl. Agu main field on the other hand is in Block OPL-277 which is located in Imo state. The reservoir’s porosity is within the range of 25% to 32%.1. with a very low GOR of 200 to 260scf/stb. and permeability in the range of 5 to 6 Darcy. Agu 2 and Agu 3 appraisal wells were drilled which encountered several sands including sands E7000.63psia and 5158psia respectively.3.1 Introduction Okwuibome field is located in OML 143 and is situated in the northern depositional belt of the Niger Delta. Sterling has drilled some wells in the field. Okw-A well was completed in IID sands while Okw-C and Okw-B wells were completed in IVA-1 sand. the oil here is not as viscous as the oil in the IID sand. although a high GOR was encountered in E8000. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 20 . The oil gravity is between 22 and 26 degrees API gravity. and the oil is relatively viscous. The three wells were completed up dip of the reservoir. The initial pressures for OKW B and C are 4774. The reservoir quality for the IVA-1 sand is also good with the porosity ranging from 23 to 25% and an effective permeability of 148 Darcy. Hydrocarbon from the IID reservoir has 19°API gravity with Gas Oil Ratio (GOR) of about 6scf/bbl. E7500 and E8000.1 DETERMINATION OF FLUID TYPE AND CONTACTS FROM PRESSURE-DEPTH PLOTS 3. as well as obtain fluid samples for Pressure Volume Temperature (PVT) analysis. It was later replaced by the formation interval tester and then the repeat formation tester in 1975. When this tool was first introduced in 1955. B. it was specifically supposed to collect reservoir fluid samples but could only collect one sample per trip in the well. produced their own versions. The gamma ray curve provides lithology Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 21 . later oil servicing companies such as Baker Hughes. E7000. E7500 and E8000 wells respectively. The results from this survey were compared with logs that were measured while drilling. Schlumberger’s MDT tool offers significant improvements in pressure measurement with the introduction of the combinable quartz gauge (CQG) and it also offers improved sampling capabilities.Modular Formation Dynamics Tester (MDT) survey and sampling were carried out on three wells. (See Figure 1). The formation tester was first introduced by Schlumberger. E8000 in Agu field. OKW-A. resistivity log. The purpose of carrying out this survey was to identify the fluids in the reservoir and their contacts. C and E7000. Halliburton etc. Formation testers were introduced about 55 years ago for the sole purpose of sampling fluids in the well. OKW-B and OKW-C in Okwuibome field and on three wells. E7500. Figure 1: The transition of formation testers over the years The Schlumberger MDT tool was used for pressure survey and fluid sampling in OKWA. Presently. Some of the logs used were the gamma ray log. etc. as the plot is almost linear. In the oil zone. there is a large separation with neutron on the right and density on the left.438psi/ft for water.1. etc) always exist in the sands/sandstone. From the Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 22 . Here the neutron curve shifts to the left while the density curve shifts to the right. wherever there is a drop in resistivity in a sandstone region. The densities of the hydrocarbons have opposite effects on these two measurements. The neutron-density curve on the other hand indicates the exact type of hydrocarbon in the sandstone by measuring their densities. Determine the position of the gas/oil and oil/water contacts from pressure-depth plots.404psi/ft for oil and 0. As a result. This separation is called the gas separation. it means that that point is a hydrocarbon-water contact/oil-water contact. The pressure gradients are close because the density of the oil is almost up to that of the water. the resistivity reading in a water zone is usually lower than the resistivity reading in a hydrocarbon zone. This trend is seen on the pressure plot.1. the separation that occurs is the inverse of what happens in the gas zone. So. resistivity curve. 3. Evaluation 3. Evaluate samples obtained for PVT analysis. the two measurements are plotted on a graph in such a way that the two curves overlap in the water-bearing zone.information such as sandstones and shales. In the gas zone.1 OKW-A Reservoir: the pressure plot of well OKW-A showed OWC at 1691m TVD SS and the pressure gradients calculated were 0. Hydrocarbons from petrophysical interpretation of the composite logs (gamma ray curve. neutron-density curve. Low gamma ray reading indicates sandstone while high gamma ray reading depicts shales.1. Resistivity curve gives an idea of fluid types contained in the sandstone.3.2 • • • 3. the two curves nearly overlap each other while in shales.3 Objectives Identify fluids from their pressure gradients. Since water is a conductor of electricity and hydrocarbons are insulators. from 1679m to 1772m shows sandstone because of the low gamma ray reading in that section. 0.5m. hexane.2m (see figure 2). the gas is gas condensate which is a low density mixture of hydrocarbon liquids e. The neutron-density curve for OKWB is not accurate because of the scaling that was used.3. etc. The neutron-density curve at that section shows that the density of the oil is close to that of water because the overlapping of the curves is almost the same. (see Figure 3). it means that the OWC is at 1691. Therefore. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 23 . while the oil is volatile oil. heptanes. On the gamma ray curve.1.149psi/ft for gas.215psi/ft for oil and 0. Figure 2: MDT for OKW-A Reservoir 3. pentane. the OWC is at 3134.pressure gradient calculated. On the resistivity curve. there is a sharp resistivity drop at 3134.2m and since hydrocarbon has a higher resistivity than water.2 OKW-B Reservoir: the pressure plots showed OWC at 3130m TVD SS in OKW-B and the pressure gradients calculated were 0. From the pressure gradients calculated.g. from that section. from 3118m to 3154m is sandstone because of the high gamma ray reading in that section.457psi/ft for water. the oil is heavy oil.5m. This can only mean that from that point of the resistivity drop downwards is a water zone. On the gamma ray curve. The resistivity curve at that section indicates a resistivity drop at 1691. (see Figure 4).1. from 3152m to 3196m is sandstone because of the high gamma ray reading in that section.42psi/ft for water. This means that from the point of the resistivity drop downwards is water zone. On the gamma ray curve. there is a sharp resistivity drop at 3166. On the resistivity curve. It can also be called clean oil or good quality oil. The neutron-density curve for OKW-C is not accurate because of the scaling that was used. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 24 .3 OKW-C Reservoir: the pressure plots showed the OWC at 3159m in OKW-C and the pressure gradients calculated were at 0. Therefore.234psi/ft for oil and 0.5m.5m. the OWC is at 3166.Figure 3: MDT for OKW-B Reservoir 3.3. The pressure gradient for oil shows that it is volatile oil which is oil that evaporates rapidly and doesn’t leave stains. from that section. The gradient calculated for the gas classifies it as dry gas.1.4 E7000 Reservoir: Based on the MDT pressure measurement. a pressure gradient of 0. see figure 5. the gas and water gradient were determined as 0. Figure 5: MDT for E7500 reservoir Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 25 . This gradient value indicates that the oil is heavy oil.45 psi/ft. The MDT data was unable to infer contacts due to poor pressure data obtained in the oil column.089 and 0.Figure 4: MDT for OKW-C reservoir 3. In the oil column.39 psi/ft was determined from fluid sample.3. and 0.36. Figure 6: MDT for E7500 reservoir Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 26 .1. for gas. oil and water).5 E7500 Reservoir: Three fluids were present in this sand (gas. The GOC was at 1768 m-ss and OWC was at 1774 m-ss.05.43 psi/ft. The gradients were calculated from the pressure plots to be 0. 0.3.3. These gradients show that the gas is dry gas and the oil is black oil. oil and water respectively. 36. The gradient for the oil defined it as heavy oil.3. Based on the slopes generated from the pressure plots. which gave knowledge of the hydrocarbon categorization.6 E8000 Reservoir Two fluids were present in this sand (oil and water).3.1.4 Conclusion The pressure gradient calculated from the plots helped in identifying the fluid types present in the reservoir.45 psi/ft. The fluid contact within the reservoir was defined as. It is important for the water contact to be known during the early stages of field development. Figure 7: MDT for E8000 reservoir 3. the fluid gradients were calculated as 0. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 27 . for oil and water respectively. and 0. OWC at 1815 m-ss.1. PRESSURE VOLUME TEMPERATURE ANALYSIS Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 28 .4. After the transfer. the following tests were performed on the reservoir fluid sample: • • • • • differential liberation test flash expansion test viscosity test compositional analysis pressure-volume relation These tests help in determining reservoir fluid properties which are very important in petroleum engineering computations such as material balance calculations. Schlumberger transported the reservoir fluids which they had collected in their pressurized sample chamber to Reservoir Fluid Laboratory (in PH) for full PVT analysis.1 PVT ANALYSIS OF FLUID SAMPLES GOTTEN FROM AGU FIELD Introduction MDT samples were taken from Agu 2 and Agu 3 in reservoir E7000. E7500 and E8000 for laboratory PVT analyses.4.1 4. the samples were transferred from Schlumberger’s sample chambers to the RFL (Reservoir Fluid Laboratory) cylinder in order to relieve Sterling of the rental charges that would have been incurred. At the laboratory. • • • 4.1. reserve estimates.2 • • • oil formation volume factor solution gas oil ratio viscosity Objectives bubble point pressure of the reservoir. inflow performance calculations and numerical reservoir simulations. Some of these reservoir fluid properties include. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 29 . From the site. formation volume factor and solution gas oil ratio viscosity composition of the reservoir fluid To determine the.1. Table 1 shows the results of the differential liberation test for reservoir E7000 with initial pressure at 2514psia and bubble point pressure at 1832psia.01289 0.261 4.11 1.5677 0. deviation factor.01417 0.6146 0.8473 0.971 0.01473 0.938 10.103 1.8504 0.01324 0.953 0.0000) Gas Viscosity (cp) Liquid Phase Density (gm/cm3) 0. therefore.12 1.067 1.054 1.8695 0.01268 0.8733 0. specific gravity gas.034 1.5741 0.01367 0.431 3.8434 0.989 1 215 215 215 215 215 215 215 215 181 146 111 74 35 12 0 0 34 69 104 141 180 203 215 0.116 1.108 1.4.5683 0.936 2.8583 0. liberated gas oil ratio.8821 Table 1 The PVT parameters used on the field depends on the surface separation conditions. It can also be seen that for every pressure change.121 1.09 1.01254 Liberated Gas-oil Ratio (scf/stb) Specific Gravity Gas (Air = 1.8454 0.8412 0.079 1.57 0.8375 0.104 1. gas viscosity and liquid phase density were measured. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 30 .849 0.568 0. DIFFERENTIAL LIBERATION TEST AT 157 °F Gas Volume Pressure Factor Z Solution (psia) FVF (Bo) (bbl/mscf) (Z = PV/NRT) GOR (scf/stb) 5000 4500 4000 3500 3000 Pi 2514 2000 Pb 1832 1500 1200 900 600 300 100 15 1.588 0. the formation volume factor.758 207.324 0.8384 0.113 1.106 1.1. gas volume factor.934 0.8637 0.3 Results The differential liberation test simulates the behavior of the reservoir fluids in-situ during pressure depletion.8475 0.046 1.938 0. the result of the differential liberation test was adjusted to surface separator conditions at 300psia and 100°F because the highest shrinkage factor was achieved at this pressure and temperature during the separator flash expansion test.061 30.8535 0.944 0. solution gas oil ratio. Bofb = Separator flash formation volume factor Bodb = Bubble Point Oil formation volume factor from differential liberation Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 31 .033 Solution GOR.121bbl/stb Rsif = 212scf/stb Rsid = 215scf/stb Where. Bobf = 1. scf/stb 212 212 178 143 108 71 32 9 0 Table 2 The values were adjusted using the Lee and Gonzalez method which is represented by the equation below: Bo = Bod [Bobf/Bobd] Rs = Rsif – (Rsid . bbl/stb 1.053 1.Rsd) [Bobf/Bobd] For reservoir E7000. psi 2514 1832 1500 1200 900 600 300 100 15 FVF.102 1.120 1. ADJUSTED VALUES Pressure.Table 2 shows the adjusted values for the oil formation volume factor (FVF) and solution gas oil ratio for reservoir E7000.045 1.078 1.089 1.120bbl/stb Bobd = 1.066 1.115 1. Bod = Formation volume factor at pressure from differential liberation Bo = Adjusted formation volume factor Rsif = Separator flash solution gas oil ratio Rsid = differential liberation solution gas oil ratio Rsd = Solution gas oil ratio at pressure from differential liberation Rs = Adjusted solution gas oil ratio The formation volume factor and solution gas oil ratio of reservoir E7000 was plotted against pressure in figure 1. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 32 . the expansion is relatively small. This plot shows that Bo increases slightly as the pressure is reduced from initial to bubble point pressure which is due to the fact that the liquid expands and since the compressibility of the undersaturated oil reservoir is low. The initial value of the oil formation volume factor. To show the effect of viscosity on the oil with respect to the solution gas oil ratio. This means that initially 1. This ratio is actually favorable since Boi is close to unity which indicates that the oil contains hardly any dissolved gas and reservoir volumes are approximately equal to surface volumes. Boi is 1. See figure 1.115rb/stb of oil plus its dissolved gas will produce one stb of oil.115rb/stb which increases to 1. The initial solution gas oil ratio is relatively low at 212scf/stb which indicates that the oil in reservoir sand A is black oil.120rb/stb at the bubble point pressure. Figure 2: Viscosity-pressure relationship for reservoir E7000 Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 33 . the viscosity values were plotted against pressure as shown in figure 2.Figure 1: figure showing the formation volume factor and solution gas oil ratio of reservoir E7000 The oil can dissolve more gas if available. when the oil becomes saturated. then the initial value of the solution gas oil ratio must remain constant at 212 (scf/stb) until the pressure drops to the bubble point. 5746 0.01423 0.8822 Gas Volume Pressure Factor (psia) FVF (Bo) (bbl/mscf) 5000 4500 4000 3500 3000 Pi Pb 2572 2105 1800 1500 1200 900 600 300 100 15 1.01551 0.8510 0.01372 0.099 1.8725 0.8450 0.996 0.01259 Liquid Phase Density (gm/cm3) 0. DIFFERENTIAL LIBERATION AT 159°F Liberated Solution Gas-oil Specific Gas Z GOR Ratio Gravity Gas Viscosity (Z = PV/NRT) (scf/stb) (scf/stb) (Air = 1.8472 0.970 0.123 1.075 1.At the initial pressure.063 1.8492 0.882 207. However.01293 0.5677 0.928 0.6084 0. the viscosity increases which is as a result of the fact that the gas comes out of solution with the oil thereby reducing the oil’s mobility. the viscosity of the oil is low because it is undersaturated with gas at this point.413 3.119bbl/stb Bobd = 1.114 1.8402 0.950 10.0000) (cp) 246 246 246 246 246 246 246 1. The differential liberation test was also performed on the E7500 reservoir fluid samples that were taken to the laboratory.990 1.8560 0.111 1.5684 0.051 1. the values of the formation volume factor and the solution gas oil ratio had to be adjusted to meet surface separator conditions.01482 0.5693 0.938 0. but at bubble point pressure.8757 0. Table 2 below shows the details of the test.01277 0.917 0. For this reservoir.5629 0.5862 0.252 4.088 30.952 0.8428 0.8525 0.907 2.120 1. Bobf = 1.087 1.8616 0.034 Table 3 The result of the differential liberation test was adjusted to surface separator conditions at 300psia and 100°F because a higher shrinkage factor was achieved at this pressure and temperature during the separator flash expansion test.107 1.109 1.01328 0.907 0.044 1.5690 0.572 1.000 213 178 144 108 73 36 13 0 0 33 68 102 137 173 210 233 246 0.117 1.112 1.8508 0.8449 0.123bbl/stb Rsif = 241scf/stb Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 34 .8672 0. Rsid = 246scf/stb Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 35 . psia bbl/stb scf/stb 2572 2105 1800 1500 1200 900 600 300 100 15 1. FVF.119 1. ADJUSTED VALUES Solution Pressure. It can therefore be deduced that the initial formation volume factor of 1. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 36 .083 1.030 241 241 208 173 139 103 69 32 9 0 Table 4 In reservoir E7500. Bo increases slightly.071 1. This effect is due to the fact that the liquid expands and since the compressibility of the undersaturated oil reservoir is low. as the pressure is reduced from initial to bubble point pressure.108 1.095 1.040 1.These values were used to calculate the adjustment is shown in table 4.116 1.047 1. GOR.116rb/stb of oil plus its dissolved gas will produce one stb of oil as shown in figure 3.059 1. the expansion is relatively small. The viscosity of the E7500 sample was measured and a graph of viscosity against pressure was plotted as shown in figure 4. The oil in reservoir E7000 is black oil because the initial solution gas oil ratio is low and within the GOR range for black oil. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 37 . the oil is undersaturated with gas.Figure 3: figure showing the formation volume factor and solution gas oil ratio of reservoir E7500 Furthermore. see figure 2. which means it could dissolve more gas if it were available. when the oil becomes saturated. then the initial value of the solution gas oil ratio must remain constant at 241 (scf/stb) until the pressure drops to the bubble point. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 38 .Figure 4: Viscosity-pressure relationship for reservoir E7500 The viscosity pressure relationship in figure 4 exhibits a similar trend with E7000 reservoir but the rate at which the viscosity increases in E7500 is lower. This is because the solution gas oil ratio of the oil in reservoir E7500 is higher than that of reservoir E7000. 7252 0.675 1.5882 0.6012 0.982 1.01722 0.01054 0.274 1.0000) FVF (Bo) (bbl/mscf) 5000 4820 4520 4128 Pi Pb 3887 3514 3000 2500 2000 1500 1000 500 110 15 1.5914 0.7459 0.7949 1. Bobf = 1.995 1. The values that were used to calculate the adjustment for this reservoir are as follows. Table 3 shows the results of this test in detail.7079 0.5992 0.794 0.5959 0.7337 0.6137 0.463 1.7037 0.01247 0.7195 0.6602 0.5830 0.026bbl/stb Rsif = 1476scf/stb Rsid = 1854scf/stb Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 39 .814 0.381 0.376 1.827 0.770bbl/stb Bobd = 2.008 2.962 1.971 1.026 1.865 0.1956 2.7591 0.000 1854 1854 1854 1854 1854 1854 1455 1161 920 709 522 342 158 0 0 399 693 934 1145 1332 1512 1696 1854 0.6822 0.01523 0.750 2.01996 0.905 0.188 1.707 5. a differential liberation test was conducted for the E8000 reservoir fluid sample.561 1. DIFFERENTIAL LIBERATION AT 161°F Liberated Gas Volume Solution Gas-oil Specific Pressure Factor Z GOR Ratio Gravity Gas (psia) (Z = PV/NRT) (scf/stb) (scf/stb) (Air = 1.070 0.817 1.381 208.665 27.7525 Table 5 The values of the formation volume factor and solution gas oil ratio were adjusted to surface separator conditions at 300psia and 100°F which resulted in the values shown in table 6.02344 0.965 1.997 2.292 1.793 0.7254 0.Finally.839 0.436 0.0077 Gas Viscosity (cp) Liquid Phase Density (gm/cm3) 0.6377 0.01376 0. 935 1476 1476 1127 871 660 476 312 155 0 0 These adjusted values were then plotted against pressure as shown in figure 5.754 1. Figure 5: figure showing the formation volume factor and solution gas oil ratio of reservoir E8000 In reservoir E8000.364 1.587 1. psia 3887 3514 3000 2500 2000 1500 1000 500 110 15 ADJUSTED VALUES FVF. Solution GOR.038 0.754bbl/stb to 1.Pressure.202 1.754 reservoir barrel of oil plus its dissolved gas will Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 40 .129 1.278 1. the change in the formation volume factor is from 1.770bbl/stb which means that 1. bbl/stb scf/stb 1.770 1.463 1. Figure 6: Viscosity-pressure relationship for reservoir E8000 The viscosity of E8000 at initial pressure and at bubble point pressure is almost the same. a graph of viscosity versus pressure was plotted using the measured viscosity values of the sample and the corresponding pressure. Boi is not close to one and this implies that there might be a significant amount of gas dissolved in the oil. so even at bubble point pressure the gas that leaves the oil will have very little effect on the viscosity change of the remaining oil. The solution gas oil ratio is relatively high at 1476scf/stb which indicates that the oil present in the reservoir sand is volatile oil. In addition. the more volatile the oil. See figure 6. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 41 . In this same reservoir. so the reservoir has to be conditioned properly to ensure that a representative fluid sample is obtained. Also. in this reservoir sand.produce one stb of oil. Rsi is constant at 1476scf/stb from the initial pressure to the bubble point pressure. But on the other hand. see figure 5. (figure 5). the farther away Boi is from one. This is because the oil is undersaturated with gas and has the capacity to dissolve more gas. This could be a result of the high solution gas oil ratio. 4.1.4 Conclusion The results of the PVT analysis are important in completion designs.how the completion strings will react to the produced fluids. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 42 . On the other hand. it helps in deciding the type of surface facilities to be used for separation when the fluid is eventually produced to surface. Flow couplings should be installed above and below landing nipples or any other restriction that may cause turbulent flow. APPENDIX Tools Flow coupling Flow couplings are designed to inhibit erosion caused by flow turbulence.5. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 43 . Selective landing nipple Selective landing nipple is a completion component fabricated as a short section of heavy wall tubular with a machined internal surface that provides a seal area and a locking profile designed to be run in series throughout the wellbore. using standard wireline methods to provide communication between the tubing and the tubing/casing annulus. Tubing seal divider The tubing seal divider is designed to disconnect the tubing string without disturbing the packer setting.Sliding sleeve The sliding sleeve is comprised of fullopening devices with an inner sleeve that can be opened or closed. Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 44 . Blast joint Blast joints are installed in the tubing opposite perforation wells with two or more zones. The blast joints are sized to help prevent tubing damage from the jetting action of the zone perforations.No-go landing nipple No-go landing nipple is a nipple that incorporates a reduced diameter internal profile that provides a positive indication of seating by preventing the tool or device to be set from passing through the nipple. Packer Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 45 . injection or treatment. A typical packer assembly incorporates a means of securing the packer against the casing or liner wall.A packer is a downhole device used in every completion to isolate the annulus from the production conduit. Packers are classified by application. typically by means of an expandable elastomeric element. setting method Students Industrial Work Experience Scheme (SIWES) with SEEPCO 06/2011 to 10/2011: Adaeze Eloka 46 . and a means of creating a reliable hydraulic seal to isolate the annulus. such as a slip arrangement. enabling controlled production.