石油实验地质

2015, 37(S1): .

Abstract(286) PDF-CN(498)

Abstract:

Logging identification of Ordovician karst cave filling in the Tahe Oil Field

Qin Weiqiang, Sun Zhaohui

2015, 37(S1): 1-4. doi: 10.11781/sysydz2015S1001

Abstract(802) PDF-CN(564)

Abstract:
The SINOPEC Northwest Company has deployed over 1300 wells in the Ordovician in the Tahe Oilfield, among which about 1/3 of the wells turned out empty or leaking. Many wells drilled to karst caves. The caves were partially filled, and the filling materials had various physical properties. The accurate identification of the nature of cave fillings can help the deployment of completion program and select completion interval. We used core data to calibrate conventional logging, summarized the logging responses of different fillings, and identified fillings on seismic maps. The fillings of ancient underground rivers in blocks 6, 10, 12 in the Tahe Oil Field were studied.

Mixed sedimentation in the Carboniferous Xiaohaizi Formation in the central uplift of the Tarim Basin

Shang Kai, Guo Na

2015, 37(S1): 5-9. doi: 10.11781/sysydz2015S1005

Abstract(715) PDF-CN(510)

Abstract:
The stratigraphic and sedimentary facies of the Carboniferous Xiaohaizi Formation in the central uplift of the Tarim Basin were analyzed in details based on previous research and combined with outcrops, ancient tectonic sedimentary background, paleontological, drilling and seismic data. Mixed clastic and carbonate deposits widely distributed in the study area. The change of lithology assemblage in the east of the study area corresponded to the transition environment with intense clastic and carbonate mixing. We recognized three kinds of mixed sedimentary facies such as mixed tidal flat facies, open platform facies and restricted platform facies. A development model of the mixed sedimentation in the Carboniferous Xiaohaizi Formation in the central uplift of the Tarim Basin was summarized.

Characteristics of clastic rock reservoir accumulation in Avat area of the Tarim Basin

Geng Feng, Gu Weixin

2015, 37(S1): 10-15. doi: 10.11781/sysydz2015S1010

Abstract(785) PDF-CN(523)

Abstract:
Through the analyses of reservoir rock fluid inclusions in different layers of important drilling wells in Avat area of the Tarim Basin, we found that hydrocarbon charges had occurred in the Paleozoic-Cenozoic clastic reservoirs. For the Silurian reservoirs, hydrocarbon charges took place during the late Caledonian, the late Hercynian, and the Himalayan. For the Devonian reservoirs, there were two charging periods:the late Hercynian and the Himalayan. For the Triassic and Paleogene reservoirs, hydrocarbon charges took place during the late Himalayan. However, reservoirs failed to form due to the poor matching relation between hydrocarbon source and traps, poor preservation conditions, and the missing of hydrocarbon migrating faults. The analyses of source rocks and tectonic evolution history showed that, the Paleozoic carbonate and clastic rocks formed primary oil and gas pools while the Mesozoic clastic rocks formed secondary oil and gas pools in the transition zone between the Awat Sag and palaeo high. Stratigraphic and lithologic traps with oil source faults are favorable exploration targets.

Characteristics and controlling factors of the Middle and Lower Ordovieian carbonates in the 12th district of the Tahe Oil Field

Hai Tao, Yao Junbo, Li Bojie, Ding Lei, Zhang Shiliang, Liu Hongguang

2015, 37(S1): 16-19. doi: 10.11781/sysydz2015S1016

Abstract(805) PDF-CN(566)

Abstract:
The Middle-Lower Ordovician reservoir is considered the main developing interval in the 12th district of the Tahe Oil Field. Multi-phase orogeneses and karstifications are the main cause for the highly matured dissolved fissures and caves within the Middle-Lower Ordovician, which may also result in complex reservoir heterogeneity. This paper comprehensively utilizes data of seismic survey, coring, thin section, logging and laboratory test to clarify the fissure-cave reservoir characteristics within the Middle-Lower Ordovician in the 12th district of the Tahe Oil Field, and further discusses its dominating factor. The results indicate that, three reservoir types exist in the study area:cave type, fissure-cave type and fissure type. Primary pores take up only a tiny proportion in the accumulating spaces. Kart caves type occupies the majority, with the secondary fissure-cave type ranking behind. Dissolved fissure may undertake a favorable connecting conduit. Moreover, the reservoir dominating by fissure-fracture system, developing dissimilarly along the fissure-fracture system, may be controlled by multiple developing model along the paleochannel. Those findings may imply that underground-river conduit and monadnock existing in the lateral side of surface river are supreme zones for reservoir developing, while the dissolved fracture surface follows.

Application of “sedimentary facies controlled sand body” theory in remaining oil tapping of sandstone reservoirs with bottom water in the Tahe Oil Field

Liu Peiliang, Ding Minjiang, Wang Guocheng, Xu Yan

2015, 37(S1): 20-22. doi: 10.11781/sysydz2015S1020

Abstract(749) PDF-CN(673)

Abstract:
The sandstone reservoirs with bottom water in the Tahe Oil Field belong to plains of braided river facies. We studied the connectivity between channel and channel bar sand body based on the "sedimentary facies controlled sand body" theory and combined with intercalation distribution and its relationship with micro facies. By using numerical simulation, we analyzed the influence of sand body superimposition on water flooding mode and remaining oil distribution, which could guide remaining oil potential tapping during high water-cut stages.

Main controlling factors for remaining oils in horizontal wells in sandstone reservoirs with bottom water in the Tahe Oil Field

Yang Song, Liu Peiliang, He Chang, Li Dandan

2015, 37(S1): 23-28. doi: 10.11781/sysydz2015S1023

Abstract(700) PDF-CN(621)

Abstract:
In blocks no.1 and 9 in the Tahe Oil Field, complicated oil/water relationship and various controlling factors have made it difficult to tap remaining oils in sandstone reservoirs with bottom water during high water cut period. Water flooding pattern and remaining oil occurrence were analyzed in view of different controlling factors. Horizontal tracks and interlayers have four different configurations:totally blocking, horizontal to interlayers, crossing interlayers, and half blocking. The permeability of horizontal layers can be divided to four styles:two stage type, serration type, step type, and homogeneous type. Combining with production performance, we studied water flooding mode in horizontal section corresponding to different configurations and permeability styles, and discussed its control on remaining oil. Some methods for tapping remaining oil in reservoirs with bottom water were proposed.

Measurements to retrograde condensation during the middle and late production periods of condensate gas reservoirs

He Yunfeng, Yao Tianwan, Wang Ligang, Zhang Ai

2015, 37(S1): 29-33. doi: 10.11781/sysydz2015S1029

Abstract(715) PDF-CN(660)

Abstract:
For depleted condensate gas reservoirs, when bottom flow pressure in condensate gas wells is below dew point pressure, condensate oil will occur and gather in the near wellbore area gradually, resulting in not only the sharp decrease of reservoir permeability and production, but also retrograde condensate pollution, which res-tricts gas reservoir recovery. As a result, it is very important to retrograde condensation pollution in the near wellbore area. Several measurements are taken to retrograde condensation. A large amount of gas can be injected with high strength to drive oil. Gas injection huff and puff in single well can break through condensate oil wall. Acidification can improve reservoir permeability. These methods are easy and cheap to carry out, and can retrograde condensation effectively.

Application of well testing data in the Tahe OilField

Li Bojie, Hai Tao, Wang Peiyi, Luo Xianping

2015, 37(S1): 34-36. doi: 10.11781/sysydz2015S1034

Abstract(664) PDF-CN(599)

Abstract:
In the fracture intersection regions in carbonate reservoirs in the Tahe Oil Field, strong formation energy often causes water breakthrough, which is harmful for oil production. How to suppress bottom water coning is a major problem. Field works show that we can estimate in advance water avoidance height by monitoringflow pressure periodically, which can control water breakthrough effectively and prolong water-free oil production period. The wells in river dominant areas are filled severely, and big production pressure differential makes it difficult for oil production. For these wells, we should avoid filled caves and inject acid fluid to connect reservoirs. Pipe casing leaks more and more often in production, which can be found by injection profile testing. Fractured and vuggy reservoirs have strong water absorption ability, so the leaking position of pipe casing absorbs less water and shows minor changes on flow amount and temperature curves. In this situation, we can compare GR curves to find leaking position.

Deep pumping applied in water injection failed wells in fractured and vuggy reservoirs in the Tahe Oil Field

Li Anguo, Wen Bo, Su Hongtong, Wang Dong, Su Wei

2015, 37(S1): 37-39. doi: 10.11781/sysydz2015S1037

Abstract(607) PDF-CN(541)

Abstract:
The Ordovician reservoirs in the Tahe Oil Field are typical fractured and vuggy carbonate reservoirs. The superimposition of tectonic settings, karstification and diagenetic effects formed pores, caves and fractures, which served as storage spaces and migration pathways for hydrocarbons. With the deepening of water injection development, water injection failure gradually increases, and some wells have recovery rates lower than 10%. The pressure changes, injection scale and cyclic injection amount of water injection were studied to determine the reservoir type and scale for failed wells. This method has been applied in field works, and proved effective.

Some new understandings of water driving curves

Wen Bo

2015, 37(S1): 40-42. doi: 10.11781/sysydz2015S1040

Abstract(754) PDF-CN(692)

Abstract:
The application of water driving curves in the Tahe Oil Field reflects some reservoir characteristics such as reservoirs and fractures, which could guide water driving in field works. With the optimization of single well water injection, injection curves become flat in many wells, indicating for water spillover after energy supplement. The experience from these wells can guide future water injection.

Practice of acid fracture avoiding filling caves in district no.12 in the Tahe Oil Field

Ding Lei, Hai Tao, Zhang Shiliang, Ma Tao, Yao Junbo

2015, 37(S1): 43-45. doi: 10.11781/sysydz2015S1043

Abstract(624) PDF-CN(533)

Abstract:
Drilling, logging and core sample data showed that about 25.1% of wells in district no.12 in the Tahe Oil Field were filled, resulting in low production efficiency. The correspondence between logging data and different filling materials was discussed. The production of filling caves with different filling materials was studied in view of well yielding. Based on the ideal cave sequence proposing by Loucks, acid fracture avoiding filling caves was practiced in the upper broken area or the lower collapsed area to improve oil production.

Application of residual oil saturation logging data in Yakela Condensate Gas Field

Zhang Kui, Xu Shisheng

2015, 37(S1): 46-50. doi: 10.11781/sysydz2015S1046

Abstract(602) PDF-CN(572)

Abstract:
The Yakela Condensate Gas Field has been developed from 2005 and been keeping stable production for 10 years until now. It has already entered the middle-late period of development. Residual oil saturation logging has been conducted in several wells in order to monitor residual oil situation accurately, and to guide gas field adjustment. Meanwhile, the authors made an evaluation of reservoir connectivity and assisted to make a fine division of small layers by applying residual oil saturation logging data.

Residual oil in Yakela Cretaceous condensate gas reservoir

Zhang Hui, Zhang Kui

2015, 37(S1): 51-54. doi: 10.11781/sysydz2015S1051

Abstract(811) PDF-CN(596)

Abstract:
Yakela Cretaceous condensate gas reservoir is a deep gas reservoir with high temperature, high pressure, and edge water. It has been keeping stable production for 10 years until now. Since the advance speed of edge water is increasing, the water control of gas reservoir is difficult and the production is declining apparently. The gas reservoir is hard to maintain a stable situation now. By carrying out a fine contrast of small layers, and integrating with the logging information of residual oil saturation, we studied residual oil distribution, and proposed four types of residual oil:interlayer residual oil in the Upper Cretaceous, interlayer residual oil in the Lower Cretaceous, intralayer residual oil (at the bottom of upper gas layer), and water-flooded residual oil. It laid a foundation for residual oil development in the future.

Quality control and optimization of partial-stack datasets in pre-stack seismic inversion

Guo Yuan, Cao Yinxiang

2015, 37(S1): 55-58. doi: 10.11781/sysydz2015S1055

Abstract(754) PDF-CN(525)

Abstract:
High quality partial-stack seismic data are the foundation of pre-stack inversion; however, the mis-tie and the phase displacement of partial-stack seismic datasets often lead to unconfident elastic parameters. It's very necessary for seismic datasets to control quality in order to improve the reliability of different offset gathers. In the paper, partial-stack seismic could be adjusted based on the standard of threshold value of residual quasi-correlation, and then seismic processing of phase correction and limited time shift would be executed based on the method of static graphs and recursive interpolate. The actual data inversion shows that under the responsible quality control, the partial-stack datasets correction processing could improve the inversion quality obviously.

Logging techniques for horizontal wells in the Tahe Oil Field

Yin Bei, Luo Rong, Cui Guang

2015, 37(S1): 59-62. doi: 10.11781/sysydz2015S1059

Abstract(562) PDF-CN(530)

Abstract:
Reasons for logging failures in horizontal wells in the Tahe Oil Field during year 2014-2015 were discussed. There are three main problems:wet joint docking, instrument failure, and instrument blocked. Some common influencing factors in construction were listed. A set of effective construction technique and solution was proposed, including hole and construction preparation before logging, technical improvement of horizontal well logging, and avoiding accidents caused by error operation. Some corresponding solving measures were put forward in view of high temperature and high pressure in Shunnan area, and achieved good application effects.

New measurements to tap potential in the Yakela Condensate Gas Field

Sun Bolin, Wang Yongzhong, Zhang Lei, Li Ding, Lan Lin

2015, 37(S1): 63-65. doi: 10.11781/sysydz2015S1063

Abstract(640) PDF-CN(477)

Abstract:
Locating in Kuqa of Xinjiang, the Yakela Condensate Gas Field is one of the biggest equipped sandstone condensate gas reservoirs of SINOPEC. During depletion development, water content in a single well increases rapidly, and gas producing capacity decreases quickly. Water control has become difficult, and some wells stop flowing due to water flooding. Due to the limited introduction of new technology, the solution to increase production strongly depends on gas well patching holes, converting zone and water plugging, which show poor effects. Through fine adjustment, fine development of gas field, low pressure process construction, integrated liquid emission experi-ment and other actions to stabilize or increase production, the Yakela Gas Production Plant has reached good effects. A new direction is expanded to efficiently exploit oil and gas capacity of the Yakela Condensate Gas Field, which offsets the progressively decreasing production of old wells and stabilizes gas field production.

Exploration technology for fractured-vuggy condensate gas reservoirs in block 9 of the Tahe Oil Field

Zhang Wei

2015, 37(S1): 66-69. doi: 10.11781/sysydz2015S1066

Abstract(609) PDF-CN(558)

Abstract:
The Ordovician fractured-vuggy condensate gas reservoirs in block 9 of the Tahe Oil Field are characterized by complex reservoir geology and complicated seepage flow law of multi-phase fluid through porous media. The gas wells have high pressure, high paraffin content, high H₂S content and high setting points. Currently, there are few mature exploration experiences and techniques for reference.After two years' practice, several methods such as open-flow potential, binomial production equation as well as divergences comparison bet-ween gas wells are used comprehensively. The reasonable gas production rate per well in fractured-vuggy condensate gas reservoirs was determined and a depressurizing development strategy was established. Meanwhile, three anti-blocking technologies involving fluid velocity optimizing, modified paraffin removal mechanical tech-nology under high pressure and positive injection of fluid slugs were proposed. Thus, the development effect on fractured-vuggy condensate gas reservoirs has been successfully improved.

A method for the development of ultra-deep heavy oil reservoirs with dilute gas

Zhen Enlong, Cao Chang

2015, 37(S1): 70-72. doi: 10.11781/sysydz2015S1070

Abstract(604) PDF-CN(503)

Abstract:
Wells in the heavy oil producing blocks of the Tahe Oil Field are usually very deep and demand a large amount of dilute gas, yet have a low yielding rate. Conventional techniques can no longer meet production needs. Nitrogen is now applied to dilute gas injection. Injection depth, nitrogen amount, choke size and the start-up pressure of gas lift were discussed. This new method was practiced in well YQ5-1 in Yuqi area and proved successful. Blending rate decreased from 11:1 to 3.4:1, and single well yield increased from 10 t/d to 38 t/d. It saved dilute gas and raised oil production.

Causes and countermeasures for scaling and corrosion in nitrogen gas injection wells

Guo Jing, Zou Sijia, Wang Yazhou, Ma Xiaoyu, Shi Pengfei

2015, 37(S1): 73-76. doi: 10.11781/sysydz2015S1073

Abstract(819) PDF-CN(578)

Abstract:
Nitrogen gas injection in the third round of oil recovery is an effective way to improve recovery rate; however, scaling and corrosion bring serious oil development losses. The influence of injection agent on ground injection system and downhole strings was analyzed. The mixing of formation water and the low purity of nitrogen gas are the main causes for scaling and corrosion. We can reduce scaling and corrosion rates by using purer nitrogen gas, non-metallic materials and sacrificial anode materials.

Identification of well connectivity in fractured-vuggy carbonate reservoirs:A case study of Tuofutai area in the Tahe Oil Field

Liu Junling, Wang Dongzhai, Wu Hui

2015, 37(S1): 77-81. doi: 10.11781/sysydz2015S1077

Abstract(709) PDF-CN(528)

Abstract:
The Ordovician reservoirs in the Tahe Oil Field consist of large-scale seams and holes and the effective reservoir space is mainly interconnected seam and hole units. Reservoir development practices show that under the control of the distribution difference of seam and hole units, multiple independent seam and hole complexes exist within the same reservoir. Connectivity between seam and hole complex is one of the decisive factors of reservoir development effect. In order to define the connectivity between different seam and hole complexes, the author puts forward several methods based on dynamic and static data:(1) The same seam and hole complex shows high and continuous rate of seismic amplitude change. On the contrary, different seam and hole complexes show lower and discontinuous rate of seismic amplitude change; (2) Fluid within the same seam and hole complex may be similar; (3) Wells in the same seam and hole complex often show similar pressure and fluid producing change tendency; (4) A well can correspond to the drilling and maintenance measures of other wells in the same complex. Based on abundant dynamic and static data, it has been clearly analyzed whether wells in the W1 well block are connected, and a division standard for well connectivity in fractured-vuggy carbonate reservoirs has been established.

Intermittent water flooding and oil production applied in channel sandstone reservoirs during early water flooding

Liu Hongfa, Wang Fengying, Zhang Wei, Zhang Shuhui, He Xueqin

2015, 37(S1): 82-83. doi: 10.11781/sysydz2015S1082

Abstract(603) PDF-CN(525)

Abstract:
Channel sandstone reservoirs are small reservoirs with edge water, and have a strong heterogeneity both vertically and horizontally. Elastic drive is a common way in production. Water flooding is necessary during late production period because that formation pressure is insufficient. Conventional continuous flooding works well during early period; however, water breakthrough often takes place. The effect of cyclic water flooding during late period is poor. We propose a new method named "intermittent water flooding and oil production". When water is injected, oil wells stop producing until formation pressure is high enough. And then, water injection stops, and oil production goes on.

Water plugging adaptability under different water-flooding modes in Tahe bottom-water sandstone reservoirs

He Chang, Yang Song, Zhang Wei, Chen Youmeng, Li Dandan

2015, 37(S1): 84-89. doi: 10.11781/sysydz2015S1084

Abstract(565) PDF-CN(446)

Abstract:
When the horizontal wells of sandstone reservoirs with bottom water have water, their productions will fall quickly and sharply. Water flooding, as an effective measurement in horizontal well management, is restricted by water flooding extent. As a result, it is necessary to study the characteristics of water flooding and the adaptability of water plugging in horizontal wells. We studied the influence of permeability association type of horizontal sections of horizontal wells in bottom-water reservoirs of the Tahe Oil Field on the water flooding mode of oil wells. There are four flooding modes, including dot flooding, step flooding, multistage flooding and uniform flooding, according to the flooding extent of horizontal sections. Corresponding plugging techniques were proposed in view of residual oil distribution. Under the modes of dot flooding and multistage flooding, oil usually remains in low-permeability sections and is mixed with water, and multi-round water-plugging is recommended. The oil and water mixing sections will turn to the main potential sections in horizontal wells during multi-round water-plugging. Complex water-plugging with block and hydrophobicity to dig the potential is recommended.

Research and application of oil-based particle agent for water plugging

Ma Yan, Yang Yang, Yang Zongjie, Chen Youmeng

2015, 37(S1): 90-92. doi: 10.11781/sysydz2015S1090

Abstract(583) PDF-CN(507)

Abstract:
The bottom water sandstone reservoirs in the Tahe Oil Field are mainly developed by drilling horizontal wells. They have sufficient natural energy of bottom water and serious reservoir heterogeneity. Bottom water cones along high permeability zones, which makes it difficult for remaining oil recovery. Applying numerical simulation and production logging data, a conclusion was drawn that bottom water breakthrough from high permeability zones easily. Furthermore, based on earlier research, we combined particle bridging plugging with dispersed phase for the first time. Oil-based particle agents for water plugging were proposed. This technique was fairly effective in field application and worth promoting.

Improvement and application of new type open hole by-pass valve in the Tahe Oil Field

Xie Jin, Liu Lian, Fan Lingyun, Yang Kun, Zhou Shengfu

2015, 37(S1): 93-95. doi: 10.11781/sysydz2015S1093

Abstract(586) PDF-CN(531)

Abstract:
The application of MFE technique in formation tests is very common in the Tahe Oil Field; however, it is difficult to predict the formation pressure coefficient and fluid properties of exploratory wells. The chief by-pass valve of open hole is one-way sealed. It is easy to leak during well shutting when internal pressure is greater than external pressure. The assistant valve has a sleeve type structure. It might open accidentally when pressure changes due to fluid impact or perforation. As a result, oil tube and case are connected, and test fails. We replaced the chief by-pass valve by a two-way sealing valve, double the length of sealing core shaft sleeve, and remove the assistant valve. These measurements improve DTS success rate, and have been applied in field works in the Tahe Oil Field.

Self-generated acid system for the Tahe Oil Field

Hu Wenting, Dong Shenhao, He Xiaobo, Li Nan, Yang Yuqin

2015, 37(S1): 96-99. doi: 10.11781/sysydz2015S1096

Abstract(704) PDF-CN(526)

Abstract:
With the development of the Tahe Oil Field, deep and ultra-deep carbonate oil and gas reservoirs have been found and put into development. The formation of a series of unconventional acid liquid system is faced with the problem of fast reaction rate and acid corrosion. In this paper, the self-acid system of the Tahe Oil Field was studied. We made self-acid in laboratory, and tested its temperature tolerance, demulsification, corrosion, acid etched fracture conductivity and rock reaction ability. The results show that the reaction rate is slow, which can improve the efficiency of acid corrosion, increase acid pressure effect, and reduce the corrosion rate of pipes. Laboratory testing results show that the acid can be applied to the reservoirs in the Tahe Oil Field. The application in well TH10270 showed good effects.

Safety of wellbore string structure in the Tahe Oil Field

Zhang Xiao, Liu Xiaolin, Liu Lei

2015, 37(S1): 100-102. doi: 10.11781/sysydz2015S1100

Abstract(611) PDF-CN(519)

Abstract:
Tube strings sometimes broke in the Tahe Oil Field. Finite element simulation was applied to study tube string accidents, and found out that the radial depth of cracks is the main factor controlling tube string breaks. The critical lift force of different defect depth was concluded, which provided reference for site operation and tubing check. According to the analysis of thread turns, the contact stress distribution of thread engagement is of "saddle" type, and in high stress on both ends of the threaded connection, prone to fastening. By combining simulation and field experiment, we can effectively reduce tube string failures.

Countermeasures for the leakage of hydraulic feedback pump for heavy oil in the Tahe Oil Field

Cheng Ting, Tu Dong, Sui Fen, Wang Leilei, Jiang Lei, Zhao Yuan

2015, 37(S1): 103-106. doi: 10.11781/sysydz2015S1103

Abstract(621) PDF-CN(475)

Abstract:
Hydraulic feedback pumps for heavy oil leaked frequently in the production of the No.2 Oil Production Plant ever since 2012, which reduced production. The production characteristics of pump leaking wells and the features of leaking positions showed that there were two major reasons for the leakage:(1) High water cut, hydrogen sulfide existence and high salinity speeded pump leakage. (2) Unreasonable structural parameters. For example, pumps 56/38 and 70/44 leaked due to small suction valve diameter. We can solve this problem by improving inlet valve structure, enlarging inlet valve and seat sizes, and improving valve seat material.

Improvement of tail pipe devices for electric submersible pumps in the Tahe Oil Field

Xia Xinyue, Yuan Bo, Ou Xuehui, Jiang Lei, Sui Fen, Cai Lu

2015, 37(S1): 107-109. doi: 10.11781/sysydz2015S1107

Abstract(676) PDF-CN(478)

Abstract:
Tail pipe devices improve the working conditions and prolong the operating life of electric submersible pumps (ESP) in the Tahe Oil Field. However, accidents might happen when small and flat cables cross the devices, which is harmful to pumps. We found some causes through pump inspections, including cable material, compaction force, seal structure, and oil well conditions. Different small and flat cables are tested under different temperatures and seal structures. We observed their performances under same compaction force and different seal conditions, and concluded some causes for the accidents. The hanging device for tail pipes and the selection for small and flat cables were improved. The hanging device with 12 sealing rings was recommended.

Application of high-lift submersible pumps for ultra-heavy oil in the Tahe Oil Field

Zhao Yuan, Tu Dong, Jiang Lei, Cheng Ting, Cai Lu

2015, 37(S1): 110-113. doi: 10.11781/sysydz2015S1110

Abstract(528) PDF-CN(488)

Abstract:
The ultra-heavy oil reservoirs in the Tahe Oil Field are Ordovician fractured and vuggy carbonate reservoirs lack of heterogeneity. Since the level of pumping wells declines year by year, submersible pumps are recommended for heavy oil production. The application of submersible pumps in 25 well times showed that total production, previous production mode and geological characteristics were the main affecting factors. Both waterflood index curves and geological characteristics were taken into consideration. High-lift submersible pumps can maximize the potential of ultra-heavy oil.

Eliminating water lock by nitrogen injection in condensate gas field

Yan Keju, Zeng Wei, Zhang Hui, Wu Jian

2015, 37(S1): 114-117. doi: 10.11781/sysydz2015S1114

Abstract(795) PDF-CN(565)

Abstract:
The technology of eliminating water lock by nitrogen injection is an innovative trial measure in the northern Tarim condensate gas fields. This paper described the principle of the technology, and discussed some problems such as nitrogen injection volume, well selection criterion, characteristics of construction pressure curve and when to end construction combined with practical engineering case and effect of 4 wells. It is concluded that condensate gas wells with more oil and gas, energy, interlayer, water lock, low porosity and low permeability, no plug and no leakage loss are suitable for eliminating water lock by nitrogen injection. We should end construction when pump pressure is higher than formation pressure.

Acid filtration model considering CO₂ effect and its application

Li Chunyue, Li Yongming

2015, 37(S1): 118-120. doi: 10.11781/sysydz2015S1118

Abstract(737) PDF-CN(530)

Abstract:
CO₂ generates in the course of acidizing treatment with the reaction of acid and rock, which will influence the mechanism of acid leaking. An acid filtration model considering CO₂ effect has been set up based on the conventional acid filtration model in order to study the CO₂ effect on acid liquid loss and to determine the volume of free CO₂. Simulation results showed that the volume of free CO₂ increases with increasing acid concentration and decreases with increasing pressure. In acid corrosion fractures, when free CO₂ exists, filtration law is the same as foam fracturing, and the volume of acid fluid loss reduces with increasing CO₂ volume.

Mineral insulated heating cable used in ultra-deep ultra-heavy oil wells

Cheng Zhongfu, Zhang Jianjun, Yang Zuguo

2015, 37(S1): 121-124. doi: 10.11781/sysydz2015S1121

Abstract(751) PDF-CN(515)

Abstract:
Carbonate reservoirs in the Tahe Oilfield are ultra-deep and ultra-heavy oil reservoirs. Oils stop flowing at the depth of 2000-3000 m. The conventional heating method to reduce viscosity with electric heating rods is restricted by heating depth, and fails at the depth of 2000 m. Mineral insulated cable uses continuous and high qua-lity copper wire as heat conductor and special mineral material as insulation. So, it is more effective and lighter, and can work in wells deeper than 3000 m. The mineral insulated heating cable was applied in well TH12177CH in the Tahe Oil Field. Well head temperature rose by 38℃ and the light oil saving rate increased to 56.4%.

Optimization and numerical simulation of clastic rock acidification

Zhang Xiong, An Na, Mi Qiangbo, Fang Yuyan

2015, 37(S1): 125-129. doi: 10.11781/sysydz2015S1125

Abstract(676) PDF-CN(452)

Abstract:
Acidifacation effect is not ideal in the Tahe Oil Field due to the complicated mineral compostion of clastic rock formations. We optimized the standard for well/formation selection and the formula of acid fracturing fluid. The optimized standard was applied in well YK20 in the Tahe Oil Field, and worked well. For some acidification wells, laboratory flow experiments can not be made due to the absence of core samples. In view of this, we established and solved a numerical simulation model. The calculation results were consistent with the laboratory experiment results. As a result, we can guide acidification design without laboratory flow experiments.

Research and application for wellhead multi-channel pressure testing technology

Ma Chengcheng, Zhao Yuanpu, Li Xiaoben, Zhao Xinghua

2015, 37(S1): 130-134. doi: 10.11781/sysydz2015S1130

Abstract(678) PDF-CN(489)

Abstract:
Wellhead pressure testing is an important measurement of well control in oil and gas drilling, well completion, well workover and logging. It is significant for oil and gas well control management. One new pressure testing equipment was introduced in this paper. It used multiple channels of parallel test probe instead of single pipeline pressure testing in turn. It was applied in the Tahe Oil Field, and the effect under different wellhead conditions was discussed in detail.

Hanging pump used in gas injection wells in the Tahe Oil Field

Zeng Pengpai, Du Kang, Qiu Zhengjun, Zhu Xin

2015, 37(S1): 135-137. doi: 10.11781/sysydz2015S1135

Abstract(669) PDF-CN(477)

Abstract:
Hanging pumps have been applied in wells TK7-633CH2, TK672, TK644 and TH12147 in the Tahe Oil Field. Generally there are three ways:(1) using active rods which can move up and down; (2) using acid fluid to remove blockage; and (3) adding pressure in oil tubes. Active rods which can move up and down can remove the blockage between plunger and pump barrel, and help plunger into pump barrel. Oxygen causes the corrosion and blockage of pipe string during gas injection. Acid fluid is used to wash and remove blockage. Soak cleaning with acid fluid will destroy rod, pump and pipe, hence should be avoided. We can add pressure to help plunger into pump barrel when it is blocked. The first round of hanging pump is usually difficult while the second and third rounds are easier. Old pipes often fail in hanging pump production. The second round of acid fluid washing shows a low success rate. Pumps with higher power are recommended.

Study of high-density drilling fluid used in the Tahe Oil Field

Pu Kaichen

2015, 37(S1): 138-141. doi: 10.11781/sysydz2015S1138

Abstract(761) PDF-CN(487)

Abstract:
The importance and difficulties of the application of high-density drilling fluid in ultra-deep wells in the outside district of the Tahe Oil Field were discussed from the aspect of petroleum engineering. Combined with current implement situations, we made several methods on dealing with drilling fluids which are in HTHP well-bore surroundings. Through series of control-experiments, we imitated the true surroundings down hole via a roller oven. We optimized the handling ways to fluids from gained parameters according to the experiments. The keys of successfully manipulating deep well high-density fluids are bentonite, solid phase, filtration control, system's rejection capability and stability.

Application of acid and sand fracturing in carbonate reservoirs

Wang Jianning, Zeng Dayong, Qiu Youxin

2015, 37(S1): 142-144. doi: 10.11781/sysydz2015S1142

Abstract(631) PDF-CN(493)

Abstract:
The Tahe carbonate reservoirs are marine facies reservoirs on land buried over 5000 m deep. The formations are featured by high pressure and high temperature, and the reservoirs are fractured and vuggy ones. Most wells only produce after acid fracturing. But some wells achieve productivity by acid refracturing not long after completion due to high closure pressure. In recent years, Tahe oilfield improved fracture conductivity by sand-adding acid fracturing. But the high pressure during sand-adding may cause dangers, and the success ratio of sand-adding is low. By research and exploration, injecting pre-acid during sand-adding acid fracturing achieved good effects.

2015 Vol. 37, No. S1

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