The so-called extended reach directional well refers to a directional well whose ratio of horizontal displacement to vertical depth is greater than 2, and usually a directional well whose ratio is close to 2 is also called extended reach well. Extended reach drilling technology is developed on the basis of directional well technology.
China Offshore Oil began to drill cluster directional wells in Bohai Bay from 1968. At that time, the orientation tool was turbodrill+elbow joint+centralizer, and the orientation was calculated manually by the marking method of ground drill. It is low in accuracy, low in efficiency and high in risk to record well deviation and azimuth by pulling out every single or every column in the deflecting section. Only after the deviation building reaches the designed maximum deviation can the deviation stabilizing drilling tool be used for drilling. From 1968 to 1975, this unique technology was used to drill dozens of directional wells on multiple platforms in Bohai Sea, which made the offshore cluster well drilling technology at the leading level in China at that time.
From 65438 to 0976, single-point camera inclinometer and DYNA downhole power screw drilling tool were imported from abroad. From then on, downhole orientation replaced ground orientation, improved orientation accuracy and drilling efficiency, and made directional drilling technology reach a new level.
1979, using new directional tools, we drilled 12 directional wells on Bohai Platform 8, with an average well depth of 332 1m, the maximum horizontal displacement of 1 184m, and the average well construction period of 55 days, which created a new domestic level.
After 1980, China Offshore Oil entered the period of large-scale oilfield development, and advanced directional tools were introduced one after another. During 1982, Dana and NAVI drilling tools and cable inclinometer (DOT) were used in directional wells in Chengbei Oilfield, Bohai Sea, which further improved drilling efficiency. There are 28 directional wells in Platform A of Chengbei Oilfield, with an average well depth of1.857m and an average well construction period of 1.7 days.
From 1985 to 1989, advanced instruments such as wired inclinometer SST, electronic multipoint inclinometer, anti-magnetic interference inclinometer (SRD), gyro inclinometer (BOSS), cable-free inclinometer (MWD) and drilling tools of Dyna and Neville were introduced successively, which made the directional tools reach the international level. And train directional drilling personnel at home and abroad to make offshore directional drilling technology enter a modern level. By the end of 1990s, hundreds of directional wells had been completed in Weizhou 10-3, Bozhong 28- 1, Jinzhou 20-2, Suizhong 36- 1 and other oil and gas fields, many of which were highly deviated wells and extended reach wells. 199 1 ~ 1992 respectively drilled two horizontal wells, Bozhong 28- 1-N6H and Weizhou1-4-a13.
During the period of 1993, CNOOC North-South directional well professional team merged and established offshore directional well technical service company, which further strengthened technology introduction and development. AKO and Land mark directional well application software have been introduced successively, and the technologies of directional drilling, three-dimensional extended reach drilling and horizontal well have been overcome, and breakthroughs have been made, making the technical elements of directional drilling complete.
Firstly, the steering drilling combination is improved, PDC bit+high-power steering motor with adjustable bending angle (AK0)+ inclinometer while drilling (MWD). Secondly, a group of experienced and advanced directional well engineers have been trained by using the special directional well computer software package, which has laid a foundation for the application of directional drilling technology. Since 1995, steering technology has played an obvious role in high-quality fast drilling and dense cluster drilling.
Based on the mature application of steering drilling technology, LWD was introduced, which made the steering technology enter the geological steering drilling stage, and achieved good results in the drilling of many horizontal wells in Pinghu Gas Field, etc.
With the mature directional drilling technology, it has laid a solid foundation for extended reach drilling technology, and made offshore oil extended reach drilling technology win one after another (table 1 1- 1).
Table 1 1- 1 Statistics of offshore extended reach wells in China (as of 2002)
1 .xijiang24-1Development Technology of Extended Reach Well in Oilfield
Xijiang 24-3 Oilfield is located in the Pearl River Mouth Basin in the northern South China Sea, with a water depth of 100 m, and is jointly developed by China Offshore Oil Corporation, Phillips Company and Pecton Company. Xijiang 24- 1 Oilfield is located 8 kilometers east of the oilfield, with an oil-bearing area of 4.2 square kilometers, proven geological reserves of 465 × 104m3 and buried depth of 2,500 ~ 2,800 meters. It was discovered by 1985. It is found that the daily oil production of this well is 1905 m3, and the oil production index is as high as 370 m3/d MPa, which has the advantages of high permeability, good fluidity, no sand production, sufficient water energy and no water injection for oil production. However, it is of no development value to build a production platform or underwater wellhead by conventional methods. Until 1995, based on the experience of Phillips, a partner, in drilling extended reach wells in the British North Sea and the inspiration of drilling development wells with displacement exceeding 8,000 meters by BP Company, a new idea of drilling extended reach wells from Xijiang 24.3 oilfield production platform to Xijiang 24- 1 oilfield was put forward. Practice has proved that the development cost of this scheme is only 38% ~ 48% of the conventional development cost.
During the period of 1996, China Offshore Oil Corporation set up an expert group on extended reach well drilling engineering, and conducted in-depth and detailed research and evaluation on the subject of 14 in terms of reservoir simulation, feasibility of development scheme and feasibility of extended reach well. Comprehensive drilling production platform, rig load, power demand, friction, torque, measurement technical requirements, borehole stability and cleaning, drilling procedures, hydraulic parameters, etc. After repeated investigation and experimental analysis, detailed data reports were obtained. On the basis of reliable research, the drilling rig reconstruction scheme, drilling scheme and implementation scheme are formulated.
After careful organization and preparation, the extended reach well Xijiang 24-3-A 1 1 started drilling in1and was completed and put into production in June of the following year. The well depth is 9238m, the construction period is 10 1 day, the vertical depth is 2985m, the horizontal displacement is 8062.7m, and the vertical ratio is 2.70. The maximum deflection angle is 86.2, and the middle target radius is 45m. When drilling 14 sandstone reservoir in the descending section, the geological reserves increased by nearly 1 times, reaching 875× 104m3.
The well has set three world firsts: ① the maximum horizontal displacement is 8062.7 meters; ② The length of 311.1mm open hole section is 5032 m; ③ The depth of ③③MWD/LWD real-time transmitting and receiving signals reaches 9106m.
The well also set two world second records: ① the depth of the well is 9238 m; ② ② The depth of ②②244.5mm casing is 6752m.
(A) Xijiang 24-3-A 14 extended reach well drilling difficulties
A. Well depth: 9450m is designed and 9238m is actually drilled, which is unprecedented;
B "S"-shaped borehole profile makes it difficult to control borehole trajectory;
C. The open hole section is long, with the maximum length of 5032m, which makes it difficult to keep the borehole wall stable and the casing wear-resistant;
D. Complicated geological conditions: there are large sections of water-sensitive mudstone and shale, faults encountered during drilling and stress sections of sandstone and mudstone;
E. The bull's-eye diameter is required to be high: the design 152m, and the actual diameter is 90m.
F. The hole deviation is large (the maximum design deviation is 79. 14, and the actual deviation is 86.2), and the open hole is long, so it is difficult to clean the hole;
G. difficulty in safe cementing and completion;
H the equipment needs long-term high-load operation, with the maximum torque of 69147n m, the maximum hook load of 3825kN, the maximum derrick load of 680t, the maximum displacement of 5.7m3/min and the maximum pump pressure of 47MPa.
Although the well was difficult, with the joint efforts of experts, the drilling operation was successfully completed and put into production. After putting into production, the daily output of crude oil is stable at around 1000t, and the total investment of 226 1000 USD is recovered in more than half a year.
Encouraged by the success of Xijiang 24-3-A 14 well, from 1999 to 2002, four extended reach wells were drilled from Xijiang 24-3 oilfield platform to Xijiang 24- 1 oilfield, with a depth of 8610 ~ 9/kloc-.
(2) New technology and new technology
The application of new technology and new technology has played a key role in the success of Xijiang extended reach well. The main new processes and technologies adopted are as follows.
1. Guide tool
(1) ①TRACS and AGS can remotely control the variable diameter stabilizer; (2) A new type of extended inner nozzle guide motor; ③ Automatic steering system for rotary drilling; PDC high-efficiency gage bit is specially made by "PowerDrive" rotary steering tool, which is suitable for drilling in soft and hard formations and can be used for reverse reaming. ⑤ Hydraulic booster system.
2. Tools and techniques for reducing friction/torque
① software for monitoring and calculating torque/friction; ② Soft torque rotating system; ③ Non-rotating drill pipe protector (NRDPP); ④ Direct reading torque indicator; ⑤ Low torque and low friction drilling tools; ⑥ WOB torque joint.
3. Measuring instruments and technologies
① High-precision differential oscillometric gyroscope; (2) Ideal (signal display system for comprehensively processing drilling and logging on the ground); ③MWD/LWD, (CDR+ and) /APWD and other multi-link measurement while drilling and continuous pulse effective transmission technologies; ④ Near-bit well deviation/azimuth measurement technology (AIM); ⑤MWD's "zero gap pulse generator" and FSK(6BPS) new technology; ⑥ Drill pipe transfer logging tool.
4. Cementing tools
① Floating coupling of casing; ② Roller casing centralizer and spiral casing centralizer; ③ Self-sealing casing circulating joint; ④ Cutable casing shoes; (5) Inclined shaft rotatable liner hanger.
5. Drilling fluid and others
① Low toxic oil-based drilling fluid; ② Software for monitoring equivalent annular density (ECD) and annular velocity (MTV) of mud; ③ Advanced solid control system; ④ Hydraulic mud blowout preventer and vacuum suction device on the drilling floor; ⑤ High torque φ 140mmS- 135 drill pipe; ⑥ Mechanical Efficiency and Analysis Software Package (MEL); ⑦ Sticking prediction software package (SPIN).
2. drilling technology of extended reach wells in Qikou 17 ~ 2 and Qinhuangdao 32-6 oilfields
Bohai Qikou 17-2 Oilfield is divided into east high point and west high point, and the west high point is the main part of the oilfield. At the eastern high point 4 km away from the main body, at least 6 development wells, a jacket and 4 km long submarine pipelines need to be laid. The development cost is high and the benefit is low. Using extended reach well technology, drilling four extended reach wells from the production platform at the west high point to the east high point for development can greatly improve economic benefits.
Four extended reach wells were successfully drilled in Qikou 17-2 Oilfield at 1999. The well depth is 4435~4690m, the vertical depth is 1869 ~ 2082m, the maximum dip angle is 76 ~ 93.8, the horizontal displacement is 363 1 ~ 3697m, and the water vertical ratio is 1.77 ~ 1.94.
Based on the successful practice of extended reach well technology in Qikou 17-2 oilfield in 2006, two extended reach horizontal wells were drilled in Qinhuangdao 32-6 oilfield to develop Guantao Formation reservoir in this oilfield. It pioneered the use of extended reach well technology to develop a single reservoir, reduce production platforms and reduce oilfield development costs. According to the conventional development plan, Guantao Formation reservoir in Qinhuangdao 32.6 Oilfield needs to deploy more than 10 production wells, build a production platform, and use extended reach horizontal well technology to develop the reservoir, only two wells are needed, which not only improves the economic benefit, but also shortens the oilfield construction period.
Well Qinhuangdao 32-6-A25 has a depth of 3038m, a vertical depth of 1496m, a maximum deviation of 9 1, a horizontal section of 702m, a displacement of 1942m and a vertical ratio of 1.3.
Well Qinhuangdao 32-6-A26 has a depth of 37 15m, a vertical depth of 1492m, a maximum deviation of 92, a horizontal section of 98 1m, a displacement of 2997m and a vertical ratio of 2.0 1.
The application of new technology and equipment is the key to the successful implementation of extended reach wells in Qikou 17-2 and Qinhuangdao 32-6 oilfields.
(1) equipment
A. Purchase solid control equipment such as "HIGHG" linear vibrating screen and new centrifuge to improve solid control capability.
B ue13200 winch adopts reactive power compensation technology, which increases the load of distribution station by 700kW without adding new equipment, thus improving the hoisting capacity of winch.
C. The configuration of high strength 139.7m drill pipe not only ensures the safety of drilling tools, but also improves the annular return speed of the borehole and enhances the rock carrying capacity of drilling fluid.
(2) Drilling design
A. Cooperate with petroleum colleges to study rock mechanics and wellbore stability, and provide basis for drilling design.
B. screen and optimize the wellbore structure and wellbore trajectory with computer software.
C. A set of torque and friction prediction and analysis software has been developed in cooperation with relevant domestic units. Practice has proved that the error is less than 65438 05%, which is close to the advanced level of similar software abroad.
(3) Drilling fluid
Self-developed water-based polyol drilling fluid. It has the advantages of strong lubricity, low friction coefficient (below 0. 1), strong chip carrying performance (hot rolling recovery rate of drill chips reaches 90.7% ~ 93.2%), strong inhibition to mud shale, and no harm to the environment.
(4) Borehole trajectory control technology
A. extremely soft shallow highly deviated well technology. 300~500m interval, 444.5mm () deviation, dip angle above 70, entering the stable deviation section.
B.MWD/LWD, downhole variable diameter stabilizer and computer software technology are used to control 3D borehole trajectory. Among them, well Qinhuangdao 32-6-A26 used a self-developed variable diameter stabilizer, and the trial effect was good.
(V) Cementing and completion technology
A.244.5mm () casing adopts casing floating hoop, which smoothly passes through highly deviated interval and horizontal interval, and then runs into the predicted well depth.
B liner running technology in horizontal wells: put proper centralizers and weighted drill pipes on the pipe string near the vertical interval to increase the axial force and push the liner down.
C. open hole gravel packing technology in horizontal interval.
D. screen gravel packing completion technology.
E. casing perforation completion technology.
(6) plugging technology
Calcium carbonate is used to plug the plugging layer, which can be plugged by pickling or dissolving oil.
Thirdly, the technology of extended reach drilling has made remarkable achievements.
A. the economic benefits are considerable. The investment of drilling extended reach wells to develop oil fields is lower than that of conventional development schemes, and the economic benefits are remarkable. By the end of June, 2002, five extended reach wells in Xijiang 24- 1 Oilfield had produced a total of 256.3× 104m3 crude oil, with a total income of 330 million US dollars, a cumulative net cash flow of 65.438+200 million US dollars and a government tax of 65.438+500 million US dollars. It is estimated that the economic production life can reach 2008, the cumulative oil production can reach 28 10 barrels, the net cash flow is 230 million US dollars, and the government tax revenue is 270 million US dollars.
B. can make a significant contribution to society. Marginal oil fields account for a considerable proportion of the oil fields found in China waters. Extended reach well technology has opened up a new road for the efficient development of offshore marginal oil fields in the future, and will increase a large number of available oil and gas resources for the country.
C combined with the drilling and completion engineering practice of extended reach wells, innovative research results have been achieved in the optimization design of wellbore structure and casing string, numerical simulation and control of downhole torque/friction, evaluation and control of wellbore instability, guidance and visualization of wellbore trajectory, bit selection, drilling fluid and downhole tools. A set of drilling and completion technology for extended reach wells with China offshore oil characteristics and international advanced level has been formed, which indicates that China has entered the advanced ranks in the world by using high and new technologies to develop offshore marginal oil fields.
D expanded the influence of China Offshore Oil at home and abroad and improved its reputation. Around the drilling and completion project of Xijiang extended reach well, nearly 100 people from more than a dozen countries and dozens of oil companies and technology companies were organized and held in Shekou, Guangdong twice, which showed that the world oil industry affirmed the success of Xijiang 24- 1 extended reach well development and attached importance to technical achievements, and produced good results.