SPE-55044-PA

Sand Jet Perforating RevisitedJ.S. Cobbett, SPE, 4 Arundel Close, Passfield Liphook, Hants, GU30 7RW United Kingdom Summary Though sand jet perforating is not a new technique, it is one that has been almost forgotten, the last SPE paper on the subject being published in 1972. Unlike explosive perforating, which is literally a ‘‘one shot’’ process, sand jet perforating uses a high velocity jet of abrasive fluid to cut through the casing, cement and deep into the formation, enabling pressure, pumping time and other parameters to be varied to maximize penetration. Sand jets can penetrate much deeper than explosives, and offer a cost-efficient, safer and better-targeted alternative to hydraulic fracturing to bypassing deep near-wellbore damage. This paper is based mainly on experience in Lithuania, where, in 1995, joint venture oil companies first started field operations to complete development of small oil fields found in the west of the country ~see Fig. 1! during the Soviet era, but which had been considered as too small to develop for the Soviet Union, with giant oil fields to the east. Wells, some of which had produced on test at over one thousand barrels per day, had been left with heavy mud across open perforations, often for more than a decade. When it proved impossible to get these wells to flow again using ~western! tubing conveyed explosive perforators ~TCPs!, sand jetting was used, as has been the almost universal practice in Lithuania. The first well sand jet perforated by a joint venture company, which had yielded less than one barrel per day with ~western! TCPs, gave over 900 barrels per day when perforated with sand jets. Subsequently, one of the best producers in Lithuania, which had already been sand jetted once, was reperforated using more advanced techniques. Coiled tubing was run through the xmas tree and completion to enable the well to be sand jet perforated, with oil as the carrier fluid, underbalanced, with the well flowing throughout, resulting in a doubling of production to 800 BOPD. Though sand jet perforating is, at least theoretically, available from the main pumping contractors, it is almost unknown outside North America and the former Soviet Union, the main technical references ~Refs. 1–5! being over 30 yr old. Sand jet perforating does, however, provide a cost-effective means of passing deep formation damage and should form part of the armory of any practicing petroleum engineer. This paper aims to remind engineers of this, review the technology and suggest appropriate applications. Introduction Most of the oil and gas produced today comes from wells with cased, cemented and perforated completions. Nowadays, the perforations are almost always made using shaped-charge explosives, either run on electric line or tubing conveyed ~TCP!. In addition to punching holes through the casing, the main purpose of perforating is to pass the ‘‘damaged zone,’’ near to the wellbore, where drilling and completion operations have caused a reduction in permeability. This damaged zone, often quantified as ‘‘skin’’ from well-test analysis, typically extends from a few inches to a few feet into the formation. With modern drilling and completion techCopyright © 1999 Society of Petroleum Engineers This paper (SPE 55044) was revised for publication from paper SPE 39597, first presented at the 1998 SPE International Symposium on Formation Damage Control held in Lafayette, Louisiana, 18–19 February. Original manuscript received for review 18 February 1998. Revised manuscript received 10 November 1998. Paper peer approved 18 November 1998. 28 niques, including improved drilling fluids and ‘‘well-productivityfriendly’’ drilling practices, the depth of the damaged zone and the degree of damage ~i.e., the contrast in permeabilities between damaged and undamaged formations! can be minimized, enabling modern perforating techniques, particularly underbalanced perforating with deeply penetrating low-debris TCP guns, to obtain maximum productivity, and hence maximum value, from newly drilled and completed wells. Though most new wells can be perforated effectively with explosives, there remain exceptions. Where perforating performance is significantly reduced, usually because the formation is very hard, it may be impossible to get adequate penetration with explosives. In some wells, explosive perforation may be ineffective at passing a very deep damaged zone, perhaps due to poor drilling and completion practices or in old wells that have been left with drilling mud across open perforations. As explosives are ~literally! a ‘‘one shot’’ process, it is not practical to reperforate many times to improve penetration, as the chances of reperforating along ~and thus extending! the original perforation tunnels would be minimal. Where increased penetration has been required, this has usually been via hydraulic fracturing. In contrast to explosive perforation, perforating by high pressure fluid jets is not a one shot process. Unlike explosives, the amount of energy, and hence rock destruction, that can be achieved at one point is not fixed but can be increased by, for example, pumping for more time or at a greater pressure. Though hydraulic jet perforating with clear water or brine is used ~see Refs. 5 and 6!, more often sand has been added to the fluid to improve the penetration rate. For this reason, and because the present author has no experience in using clear fluids, this paper will refer to ‘‘sand jet perforating’’ only. Most of the technical papers on sand jet perforating have been written by engineers employed by pumping companies ~for example, Refs. 1–3, 6–9! and concentrate on the mechanical aspects of the perforating process. This paper will comment also on the productivity, and in particular the cleanup, of sand jet perforated wells. Technology, Equipment, and Operational Techniques Details of the technology, equipment and operational techniques are well described in the references at the end of this paper and will only be summarized here. Sand jet perforating uses a jet of fluid, with sand added to improve penetration rates, pumped at high pressure through a jet nozzle to cut through the casing, cement and into the formation. Though other fluids, including diesel and crude oil, have been used, usually the fluid used is clear water or a brine of sufficient weight to ensure that the well remains dead. If appropriate, the fluid may be inhibited, for example, with KCl to prevent clay swelling. A sand jet perforating tool ~see Fig. 2!, run on the end of the treating work string, carries one or more tungsten carbide jet nozzles. High pressure pumps on the surface, together with a sand blender, are used to mix and pump the water and sand. Though different operators and different service companies use different parameters, 1 lbm/gal of sand is typically used in the treating fluid. Surface pressures of up to 5000 psi are used, with jet nozzle sizes typically 1/4 in. diameter. Though some operators have used a hydraulic holddown to lock the sand jet perforating tool in position ~see, for example, Refs. 7 and 8!, others move the treating string so as to ‘‘slot’’ the casing and formation ~see, for 1064-6671/99/14~1!/28/6/$3.5010.15 SPE Drill. & Completion 14 ~1!, March 1999 were used to pump 188 GPM ~i. nozzle velocity. results were disappointing. A radioactive marker and gamma ray log were used for depth correlation. Lithuania’s largest. Geonafta were. Sand Jet Perforating in Lithuania The search for oil in Lithuania started in 1964. with one held in reserve. especially Refs. and perforated underbalanced.e. Cobbett: Sand Jet Perforating Revisited later working over all the accessible Genciai wells and also to determine well productivities. & Completion. run on the final completion. casing set through the Cambrian sandstone reservoir at 1800 to 2000 meters below the surface. are discussed in detail in the references. 1. with huge oil reserves of their own to the east. combined with the unusual hardness ~circa 13 000 psi ultimate compressive strength! of the reservoir rock. In addition to the use of sand jetting for perforating. cutting windows in casing. 180° opposed at 20 cm centers. Geonafta. with an estimated pressure drop of 3300 psi across the jet nozzles.e. 2!. penetration rate. total target penetration. as both well pressures were below hydrostatic.. and in 1998 one old well. Four holes per meter were made. some at over 1000 B/D on natural flow. with a nominal 1 lb/gal of local sand added. the state oil company of Lithuania. a joint venture between Geonafta and Svenska Petroleum Exploration AB of Sweden. API tubing work string. In 1996. 1–Oil fields in Lithuania. No. under Russian tutelage. cutting off tubing and casing and as an aid to acidizing ~see Ref. SPE Drill. together with a mixture of fresh and degraded treating and formation sand. before perforating a 30 m interval in each well. The success of this two well program was critical to the Genciai project and to Genciu Nafta. example. etc. The two workovers were therefore programed to use the largest readily available. with typically up to half an hour pumping time at each depth. in some cases for more than 10 yr. These workovers were trials to determine the most cost-effective approach to J. almost certainly the depth and degree of damage. was run on a 2 7/8 in. 14. Ref. following a visit to Belarus. it was assumed that better western explosives and perforating techniques would be effective in passing the damaged zone and allowing these suspended wells to flow again. The interrelationships between sand type and concentration. did not consider the modest finds in Lithuania before 1990 to be commercially viable. 1. Fresh water was used as treating fluid. both wells were completed and initially produced together at around two thirds of what they had on test in the 1980’s.S. A simple settling tank was used on the surface with the treating fluid being recirculated. again with good results. they left suspended a number of wells which had been tested at significant rates. 8. worked over two old wells in the Genciai oil field.Fig. Though limited details of the Belarus sand jetting results were available. precluded effective perforation with the Russian perforating charges in use.. Two large pump trucks. The sand jet perforating tool ~see Fig. 3!. Genciu Nafta. 4. via 5 3/4 in. Vol. March 1999 29 . 2!. made by a contractor from the neighboring country Belarus. 94 GPM for each jet nozzle! at a surface pressure of 3800 psi. Although the Russians. target rock type. Production figures are not recorded here. Fig. then started to produce some of these old wells.. However. with 30 min pumping time at each depth ~i. with one well producing 1000 times as much as before sand jetting ~but after reperforating with western TCP guns! and the other 14 times ~Genciai-2 and Genciai-6 in Table 1!. a contract was made for sand jetting the wells. applications include openhole jetting. Following completion of the sand jetting. as two of these wells were used as water injectors and the other two did not have valid well tests. three more old wells. in the Genciai field were reperforated with sand jets. but found that most of these wells would produce very little. nozzle diameter. As the wells had been suspended with heavy drilling mud across open perforations. however. fitted with two 6 mm jet nozzles. Typically four holes per meter are made. using a western pumping contractor and a well sorted 12/20 sand as abrasive. 1 h/m!. successful in getting wells to flow following perforation by sand jetting. 3. 2–Sand jet perforator for work string. Well tests confirmed that the wells had very high skins and. even after reperforation with explosives. In 1995. high-shot density TCP perforating guns. with the two wells together producing around 1% of what they had when originally tested in the 1980’s. and 9. pumping time. reperforated a well with sand jets in the Vilkyciai field in Lithuania.penetration BOPD before Via BOPD after Genciai-3 Genciai-2 Genciai-6 Vilkyciai-9 Brine 1. with returns and production coming up the production tubing x casing annulus. which is the penetration of the TCPs according to a computer simulation. the tubing. eventually to 800 BOPD. as mentioned above. & Completion. 8. 4. resulting in greatly reduced energy loss through the entry hole in the casing itself and a maximum penetration near to that of open-hole conditions. i. Vol. Brown and Loper’s analysis shows that for the cased-hole condition.236 6. tbg 84 0. A specially designed sand jetting tool was run on 1. compared with 15 min previously!.75 in. dP Nozzle.. the critical factor determining theoretical maximum penetration (L max .5 2900 71 15 8 in. as 30 J.S. Penetration The good results from sand jet perforating suggest that the penetration with sand jets is significantly deeper than with western TCPs. the approach of Brown and Loper ~Ref.0 4100 107 60 16 in. coiled tubing through the xmas tree and ~73 mm! completion tubing. 3–Sand jet perforating with coiled tubing. hence. 1. the analysis for the through casing perforation assumes that the jet nozzle is not moving relative to the casing and. Minijos Nafta.236 6. and 9!. and 9. March 1999 . suggesting that more aggressive sand jet perforating could improve production significantly.0 Local 1 2 7/8 in.1 Local 1 2 7/8 in. 4. not using a holddown allows much greater total penetration to be achieved. Sand Sand PPG Via GPM/nozzle Nozzle diam.G.0 3400 167 30 13 in. tbg 42 0. 1. 1. ins Nozzle diam. Vilkyciai-9 ~see Table 1!. a joint venture between Geonafta and Dansk Olie & Naturgas A/S ~‘‘DONG’’! of Denmark. 14. This movement would have created a much larger hole than with a stationary jet nozzle. By allowing this movement. to achieve a similar result.TABLE 1– TYPICAL SAND JET PERFORATING PARAMETERS Fluid S. at 400 BOPD. Brown and Loper’s analysis suggests a theoretical maximum cased-hole penetration of only 3 in. 0. Some operators deliberately move the treating string to cut slots. Though this well. by using a well sorted ~12 to 20! sand. 400 Old S/jet 800 In 1997. Using numbers typical for the sand jetting at Genciai.9 TCPs 917 Water 1. well tests indicated a high skin.0 Local 1 2 7/8 in. psi HHP/nozzle Minutes/perfn Est. No. 25 TCPs 362 Oil 0. through casing.0 3400 167 30 13 in. SPE Drill. rather than holes. Cobbett: Sand Jet Perforating Revisited the 1800 m tubing work string was not anchored at Genciai. C/T 45 0.. with the well still producing throughout. 217 Old explosive 833 Water 1. However. Another factor may be that as the intervals of sand jet perforated in Lithuania had already been previously perforated with explo- Fig. It was apparent during the job that well production was increasing.e. 3. whereas the sand jetting at Genciai must have penetrated deeper than 10 in. mm. For example. tbg 84 0. 8. by using a diesel/crude oil mixture as carrier fluid to minimize formation damage and by perforating underbalanced. the completion being packerless.75 in. In addition to the jet velocity and hardness of the target rock. had already been sand jetted by Geonafta and. Results obtained in the field appear to be better than would be suggested from a review of published laboratory and theoretical work ~see Refs.8 12 to 20 1 1. sand jet perforating tool and jet nozzles would have moved continuously in response to the cyclical and other forces resulting from the hydraulic pumping and jetting. though early penetration rates may be less than suggested by Refs. a further very significant effect is the energy lost by the jet impinging on the return fluid coming out through the restriction of the perforation through the metal casing. Though this analysis would be appropriate were a hydraulic holddown used above the sand jet perforating tool.. compared with a theoretical maximum open-hole penetration of 39 in.177 4. was the best producer in the field. that the entry hole diameter through the casing is little larger than the jet nozzle diameter. 1! suggests a sand jet penetration of only 3 in. 3. This ‘‘more aggressive’’ sand jetting was achieved by pumping for longer ~60 min. after infinite jetting time! in open-hole conditions is the diameter of the nozzle.157 4. as shown in Fig. 3. a doubling in rate. used in Genciai-3.. Cobbett: Sand Jet Perforating Revisited some new laboratory tests to be made. however. Fig. or computer simulation. Though not rigorous. not easy to design a laboratory test. This suggests that Geonafta’s approach ~15 min pumping time. 3. using significantly lower pressures than were used in Lithuania and for shorter pumping times. sives. Reference 9. and 9! describing the length and shape of sand jetted perforations in laboratory conditions. this methodology is based on comparing production results following perforation with western TCPs with those after sand jetting in the same wells. Genciu Nafta’s approach ~30 min pumping time! 13 in. a casing target could be lowered into a test well. No. and 7! in wells that had not been previously perforated.. tentative conclusions on well productivity will be presented. been reported ~for example. The relationship between pumping time and penetration is illustrated in Fig. Vol. Following the success at Vilkyciai in 1997. a review of all available relevant data has enabled a methodology to be developed for estimating the penetration of sand jet perforating in Lithuanian conditions. for example—see Table 1! yielded penetration of approximately 8 in. 5. These larger perforation tunnel diameters must enhance well productivity. and to date no such test or analysis has been made. From this limited field data. It should also be noted that published experimental data show that sand jetted perforation tunnels are much wider than those created with explosives. of penetration. 1. 7. which is based on both field results and very limited published experimental data ~Refs. The relative shapes of the explosively created and sand jetted perforations tunnels are illustrated in Fig. only three ~see Table 1! have subsequently been produced long enough to assess well productivity. 4. be emphasized. on extrapolation far outside the range of published laboratory data. as illustrated in Fig. 1. It should. 6. It should be noted that the author SPE Drill. in Refs. that models the movement of the sand jetting tool on the end of 1800 m of 2 7/8 in. and. Good results have. as the data available from the others were not quantitative!. This would enable a better estimate to be made of energy loss through the casing. pump rates and nozzle pressure drops being used on the different jobs. assuming that the sand jetting penetrated significantly deeper. tubing. Reference 9 also reports that adding nitrogen to the sand jetting fluid greatly improves penetration. 14. and that used at Vilkyciai ~60 min pumping time! 16 in. using the computer-estimated penetration of the TCPs as a reference. in diameter. by applying the approach of Brown and Loper. and then. however. via much smaller through-casing entry holes. & Completion. as summarized in Table 1. Ideally. in part. via larger through-casing entry holes. most of the laboratory data is over 35 yr old. together with some from wells sand jetted by Geonafta ~for which only the data from Genciai-3 are given in Table 1. 4. reports typical sand jetted perforation tunnel diameters of 2 to 2 1/2 in.S. as the estimates of penetration shown here are based. in the rock target. This is of particular interest as little else has been published on this. 2.. without sand ~to limit damage to the test well!. whereas explosively created perforation tunnels would be typically a 1/2 in. 5–Sand jet perforation in typical Lithuanian conditions †for 13 000 psi unconfined compressive strength „UCS… rock‡. 4–Perforating performance in Lithuania. and the size of the erosion pit created on the target measured.Fig. better reflecting field conditions. sand. 6. and then this could be jetted with water. Brown and Loper’s theoretical approach was then used to estimate penetrations using sand jet perforating parameters different from those in the reference wells. However. perhaps doubling early time penetration. 4 and Fig. that penetration is not a function solely of pumping time. hence. Productivity of Sand Jetted Wells Of the six wells sand jetted by the author. in response to the forces resulting from the pumping and movement of the sand jetting tool uncentralized in the casing. the existing through-casing holes may have provided return paths for much of the sand jetting fluid. It would be desirable for J. on rock targets much softer than the Lithuanian Cambrian sandstone. March 1999 31 . reducing the energy loss in through the casing. different nozzle diameters. carrier fluid. for example. however. It is. Sand jet perforating then passed the damaged zone and allowed the wells to produce once more. the same prolonged and significant cleanup was seen on the two other Genciai wells to be produced after sand jetting. by producing back these sand particles over an extended production period. & Completion. of formation damage increasing. the original perforations. in two years. Though the data quality is not as good. may be due in part to the sand jet perforating itself. Other damage mechanisms could act in a similar manner. this cleanup took approximately 2 yr. has not had access to data on any wells where sand jet perforating alone was used. No. 6–Sand jet perforating of old wells. albeit initially at very low rates. as suggested above. all the field data used here being for sand jet reperforating. and the skin down to 2. 14.Fig. this will principally be where the formation damage is particularly deep ~and severe! and where the rock is particularly hard. The wells were then left for a number of years with heavy mud across open perforations. It is suggested that the skins of newly sand jet perforated wells. though the western TCPs probably penetrated further than the Russian perforators. As shown in Fig. which typically takes only a few hours or days. The skin after sand jetting may then be partly due to sand particles entrained in the treating fluid being injected into the sand face in the perforation tunnels at high velocity and blocking pores and pore throats. Fluid invasion continued during this shut-in period. and probably also degree. lower skin and higher PI! in the majority of cases where the penetration of explosives is adequate. during which time a number of well tests have been made to enable skin and PI to be estimated. and is much more significant. the PI now being greater than when the well was first tested in 1985. Cleanup. Cleanup of sand jetted wells takes much longer. confirming that the completions were reasonably efficient. This would also suggest that explosive perforation should 32 J. for Genciai-2—the well with the best data quality—over half of the original productivity index ~PI! was recovered by sand jetting. 7–Genciai-2 cleanup after sand jetting. Over half a million barrels have since been produced from the well. 7. When the wells were tested in the 1980’s. no comparable offset data on wells that have been fracced are available.e. with the depth. the sand jet perforation tunnels do extend up to 16 in.. Sand jet perforation should therefore be used only where deeper penetration is needed than can be obtained with explosives. as no old Lithuanian wells have been fracced. Cobbett: Sand Jet Perforating Revisited produce a more efficient completion ~i. Though sand jet perforating cannot penetrate as deeply as a hydraulic frac. than the cleanup of explosive perforated wells. using Russian electric-line conveyed shaped charges. sand jetting is very time consuming and will usually cost more. Fig. into the formation. As shown in Fig. As mentioned above. Vol. this was not enough to pass the damaged zone and very little production was realized. As shown in Fig. were most probably deep enough to pass all or most of the damaged zone. In Genciai-3. SPE Drill. by which time the PI was back to 90% of what it was when it was first tested in 1986. These show clearly that the well is cleaning up over a long period of time. in the range of 17 to 35 at Genciai. 6.S. and higher at Vilkyciai. If. skins were below 10. Sand Jet Perforation Applications Compared with explosive perforation. could be reasonably assumed to occur in this instance. in the Genciai oil wells. then they probably pass most of the damaged zone. for example. 1. rather than to any preexisting formation damage. March 1999 . 6. . Some formations are so hard that the performance of explosive perforators is much less than that indicated by the manufacturer’s tests according to API RP-43. October. Lithuania’s largest oil field. The resulting.048 gal 3 3. 6. 1207 ~October 1972!. If there is sufficient oil present to justify it. J. Harriman.: ‘‘Provisional Instructions on the Hydro-Sand Jet Method of Perforation. Pittman. SI Metric Conversion Factors bbl 3 1. with the sand jetted perforation tunnels being prepacked with gravel in preparation for an internal gravel pack if sand control was required. Vol. particularly in the former Soviet Union. 413 ~May 1961!. ‘‘Hydra-Jet Data Book. AIME 222. No.: ‘‘Investigation of Abrasive-Laden-Fluid Method For Perforation and Fracture Initiation..In the former Soviet Union. He recently spent four years acting as Technical Manager for Genciu Nafta. Pet. Svenska Petroleum Exploration AB. technical report ~April 1965! Tulsa. 3 2. AIME 228. sand jetting is little known or used in the oil field. S. reservoir rock compressive strengths exceeding 20 000 psi are common in some of the deeper and more expensive wells now being drilled.54 in. He can be found at cobbett@compuserve. 489 ~May 1961!. References 1. Cobbett also gives occasional ‘‘Well Productivity Awareness Schools’’ for BP at locations worldwide.’’ Dowell Div. Brown. John. J.589 873 ft 3 3. albeit only applicable to packerless completions or wells with completion tubing large enough for the returns to pass the coiled tubing x production tubing annulus during sand jetting..’’ ‘‘tip screenout.W. 3 2. Sand jet perforating. 3. drilling. ~January 1978! Duncan. have high skins and could benefit from this approach. Lowe.. sand jet perforating could be used in some wells.’’ ‘‘short fat fracs’’!.535 924 psi 3 6. Pet. as in Lithuania.. reduction in perforation penetration can make it impossible to perforate some wells efficiently.L.S. R. but apparently unavoidable.. Pet.54 lbm 3 4. 483 ~May 1961!. D. et al. Ousterhout.’’ J. Technol. and Huitt.: ‘‘Theory of Formation Cutting Using the Sand Erosion Process. D. Cobbett: Sand Jet Perforating Revisited Acknowledgments The author thanks Genciu-Nafta UAB. 3rd Ed. P. Houston. II perforator tests has an ultimate compressive strength of around 6000 psi. 8.W. the Lithuanian-Swedish joint venture completing the development of Genciai. in a number of areas. compared with hydraulic fracturing. then these wells would. making sand jetting much less likely to damage the well by inadvertently fraccing into a water-bearing interval below. 4. typically four-fold. of the Dow Chemical Co. ‘‘Abrasijet. Many new wells suffer deep. and St. after infinite pumping time ~as defined in Ref.C.’’ The All-Union Inst. workovers and completions. passing deep formation damage.. 9.. and Henson. & Completion.S. and elsewhere. However.. Pet. SPE Drill. Technol.’’ J.’’ J. be good candidates for sand jetting.M. 5.W. McCauley. and Loper. Pekarek. 7. Trans. OK. Peters. and put back on production. without needing a rig for any more extensive workover. sand jet perforating could be a cost-efficient alternative to hydraulic fracturing or drilling additional wells. Nomenclature L max 5 maximum theoretical penetration. Also.: ‘‘Backsurging and Abrasive Perforating To Improve Perforation Performance. a number of deep.: ‘‘Field Applications of Abrasive-Jetting Techniques. is that the vertical interval treated may be closely controlled. Technol. forcing operators to hydraulically fracture them or drill additional wells to obtain production targets. completed without packers.’’ SPE paper 26583 presented at the 1993 SPE Annual Technical Conference and exhibition. Trans. However. As an alternative to limited fracs ~‘‘frac pac. without taking a well off production is an exciting new technique.L. J. 2. J.’’ Halliburton Services. 1! J.K. OK.D. meet these requirements. T. sand jetting has the capability to penetrate deeper than explosive perforators.. formation damage during drilling and completion. March 1999 33 . Abrasive Jetting Service..’’ J. via coiled tubing. Again.: ‘‘Hydraulic Jetting—Some Theoretical and Experimental Results. Conclusion Though not a new technique.C. there are old suspended wells. or a gas-bearing interval above.com. One major advantage of sand jetting. there are a large number of wells that have been suspended with heavy mud across open perforations and which now have deep formation damage.’’ SPEJ 101 ~June 1963!. expensive wells in hard formations.V.785 412 in. F. Usachev. Technol. AIME 222. 1. where explosive perforation penetration is limited. that could be reperforated via coiled tubing. 14. and should form part of the armory of every practicing petroleum engineer.L. through the completion.894 757 E201 E203 E203 E100 E101 E201 E100 5 5 5 5 5 5 5 m3 m m3 cm mm kg kPa SPEDC James Cobbett is a petroleum consultant currently working principally in well productivity. Whereas the Berea sandstone target specified for RP-43 Sec. Moscow ~June 1967!. Trans. R.: ‘‘New Well Completion and Stimulation Techniques Using Liquid Jet Cutting Technology. A. UAB Minijos Nafta and Dansk Olie & Naturgas A/S for permission to publish this paper. for Scientific Research of Oil and Gas..