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Step Description Fluid Type Average CT Rate (BPM) Time (min.) 1 Preflush (for the first stage only) Gelled Brine 2.5 ~ 3.0 20 2 Erosive Perforating Gel with Sand 2.5 ~ 3.0 12 3 Flush Gel 3 20 4 Bottoms-Up Circulation Gel 2.0 ~ 2.5 72 5 Reduce pumping rate and locate CT in the next desired depth, and repeat steps 2-5. Table 2. Pumping sequence for one stage of hydrajet perforation and the formation. Conventional methodologies had achieved only limited success in the same wells. Figure 3 shows the results from a field test showing the characteristics of the hole size and shape created with a hydrajetting tool. Fig. 2. Typical BHA schematic of a hydrajetting tool. FIRST FIELD TRIAL: HYDRAJET ASSISTED FRACTURING A number of carbonate reservoirs being developed in Saudi Arabia require a high rate of stimulation to maximize well productivity and meet field development objectives. As previously highlighted, most of the wells in these reservoirs are being drilled as open hole horizontal completions, which presents a considerable challenge when trying to achieve effective stimulation throughout the entire horizontal section, or to perform pinpoint stimulation in targeted under producing zones. The hydrajetting technology was first tested in Well A, a vertical exploration well drilled in a tight sandstone reservoir to a depth in excess of 16,000 ft. The well required hydraulic fracturing stimulation, and had similar reservoir characteristics to other wells in the area conventionally perforated. In these wells, the hydraulic fracturing attempts had to be aborted when the maximum allowable downhole pressure was reached; either before initiating a fracture or screening out prematurely early into the treatment. A hydrajetting tool was used to create long large diameter slots using abrasive jetting slurry, reducing the fracture initiation pressure. The jetting induced slots achieved deep and clean penetration with a minimal crushed zone effect, as the jetting slurry cuts through the formation and carries debris out through the CT annulus 3 . The hydraulic fracturing treatment was successfully performed in Well A. A total mass of 135,500 lbs of 20/40 ISP proppant was displaced into the formation, without any incremental tool to set nozzles precisely on target, and a jetting sub with multiple nozzles 3 . The jetting velocity of a hydrajetting tool ranges from 20,000 ft/sec to 30,000 ft/sec, exerting a pressure of approximately 4 million psi on the target zone 4 . The tool is also designed to withstand differential pressure greater than 10,000 psi and has a temperature rating of about 350 °F 5 . Saudi Aramco has successfully field tested this technique in long horizontal open hole completions. The jetting induced slots were excellent conduits of stimulation treatment fluids between the wellbore Fig. 3. Results from a field test showing the characteristics of the hole size and shape created with a hydrajetting tool (courtesy of Halliburton). 42 SUMMER 2010 SAUDI ARAMCO JOURNAL OF TECHNOLOGY
Amount of Proppant (lb) 135,600 lb 135,550 lb 140,000 120,000 100,000 80,000 60,000 40,000 20,000 0 10,637 psi 100,200 lb 17,000 psi Fig. 4. Comparison of hydraulic fracturing treatments in wells with similar reservoir characteristics. problems, at a maximum surface treatment pressure of 10,600 psi. Figure 4 shows the results of hydraulic fracturing treatments performed in Wells A, B, C and D, which were perforated with conventional perforating guns. OTHER HYDRAJETTING APPLICATIONS 0 lb Acid Stimulation in a Vertical Well 110,984 lb 11,773 psi 65,340 lb 173,000 lb 10,144 psi A B* C D Well Name Amount of Prop. Planned Amount of Prop. Placed into Formation Maximum Treatment Pressure 50,541 lb 18,000 16,000 14,000 12,000 10,000 8,000 6,000 4,000 2,000 After the first successful application of hydrajetting in a vertical well drilled in a sandstone reservoir, it was recognized by the technical team that the methodology and tools could be enhanced and used to perform pinpoint acid stimulation treatments, in both vertical and horizontal wells. Massive hydraulic fracturing acid stimulation treatments have been successfully used by Saudi Aramco to achieve multifold rate increases in vertical gas producers; drilled in carbonate reservoirs since the beginning of the gas development program. The effectiveness of such treatments has been enhanced by mixing liquid or solid diverting agents with treatment fluids, to achieve a more uniform fluid entry distribution in the multiple perforated intervals. Poststimulation surveillance data has shown effective diversion in wells, with multiple perforated intervals with close proximity. In wells with significant separation between perforated intervals, the effectiveness of diverting agents is lower. Therefore, it was decided to apply the hydrajetting technique in one of the wells — with multiple perforated intervals with significant separation — for which a matrix stimulation treatment was prescribed. The slots were created in the lower quality reservoir zones in Well E to evenly displace treatment fluids throughout all the perforated intervals. The treatment was successfully pumped and the post-stimulation gas rate achieved was about 50% higher than the pre-stimulation rate. Moreover, post-treatment logging data showed that all perforated intervals were contributing to the flow. A comparison between the pre- and post-stimulation gas rates is shown in Fig. 5. 0 Maximum Treatment Pressure (psi) Acid Stimulation in a Horizontal Well The productivity enhancement results achieved in horizontal producers when using conventional stimulation techniques (e.g., acid washes with CT and high rate bullheading treatments), have not met expectations. The effectiveness of such treatments is heavily dependent on being able to access and successfully place the treatment fluids into the targeted sections of the formation. This treatment is a challenging task, particularly in wells completed open hole in tight formations, and in cased wells with clogged perforations. The decision was made to apply the hydrajetting technique in an open hole underperforming horizontal gas producer. The slots were to be created in different zones along the long horizontal section, and then a pinpoint acid stimulation treatment at matrix conditions would be done. The treatment was successfully implemented in Well F by creating slots in the lowest quality reservoir sections along the horizontal length, and then pumping a multistage acid treatment with a diverting agent. The expectation from this approach was to maximize the ability of the acid to bypass the high quality reservoir zones and enter directly into the created fluid entry points. Post-stimulation results, Fig. 5, clearly indicate a highly successful treatment as indicated by the fourfold productivity increase achieved. Slotting a Highly Deviated Well Perforating a highly deviated cased hole, using conventional guns, run on e-Line, presents significant challenges. Most of the problems encountered are related to the yo-yoing effect experienced by the cable; due to the common tension changes found in the high angle or dogleg sections, which often result in stuck or stranded cable. Therefore, the hydrajetting technique was successfully tried, in lieu of conventional perforating, in Well G. This gas producer was drilled with a total measured depth exceeding 15,000 ft and a 73° angle. A 90 ft net pay zone was then slotted by creating three 1” slots in each of the 12 hydrajetting stages, for a total of 36 slots. A CT acid wash was then performed and the well was put into production at an initial gas rate of 20 million standard cubic Gas Production Rates (MMscfd) 30 25 20 15 10 5 0 Pre -Stim. Post -Stim. Pre -Stim. Post -Stim. Well E Production Rate Well F FWHP 2,500 2,000 1,500 1,000 Fig. 5. Comparison of pre- and post-stimulation rates for wells in which the hydrajetting technique was applied. 500 0 FWHP (psi) SAUDI ARAMCO JOURNAL OF TECHNOLOGY SUMMER 2010 43
Page 3 and 4: Summer 2010 THE SAUDI ARAMCO JOURNA
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Page 7 and 8: Stage Depth (ft) Direction Fluid Vo
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Page 11 and 12: REFERENCES 1. Moore, N.B.A., Kruege
Page 13 and 14: Next Generation Technologies for Un
Page 15 and 16: to 60 ft/hour with the hydraulic or
Page 17 and 18: improving drilling performance. The
Page 19 and 20: Robotics for Horizontal Image Acqui
Page 21 and 22: mud cap to TD at 10,100 ft. Open ho
Page 23 and 24: unning the operations by convention
Page 25 and 26: Stimulating Khuff Gas Wells with Sm
Page 27 and 28: Fig. 2. ACTive fiber optics. DESCRI
Page 29 and 30: • Treatment acid: 26% HCl acid (1
Page 31 and 32: 25 20 15 10 5 0 Well 1 Well 2 Produ
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Page 37 and 38: SAUDI ARAMCO EXPERIENCE WITH INCOMP
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Page 41 and 42: then either continue running the as
Page 43: Application of Hydrajetting Technol
Page 47 and 48: Development and Optimization of 12
Page 49 and 50: Vertical Section View 10,000 Well A
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Page 53 and 54: needed a fit-for-purpose bit design
Page 55 and 56: laboratory and previous field tests
Page 57 and 58: performances in the 12” direction
Page 59 and 60: Jaywant Verma is a Drilling Enginee
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Page 65 and 66: Fig. 6. Plot of a sidetracked (Well
Page 67 and 68: BIOGRAPHIES Izuchukwu “Izu” Ari
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