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Vol. 31 No.1， Jan. 2017

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Vol. 31 No.1， Jan. 2017

01 Diagenesis of Chang 63 reservoir and its influence on physical properties in Huaqing area of Ordos basin

ZHANG Fan et al (State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an, Shaanxi 710069)

Based on casting thin sections, SEM and X-ray diffraction tests, the research on petrology characteristics and diagenesis of Chang 63reservoir in Hua Qing area of Ordos Basin was carried out. The results show the reservoir in the study area was mainly composed of arkoses and lithic arkoses and it had little feldspar lithic sandstone. The main diagenesis includ compaction, cementation and dissolution. The compaction is the main reason of poor reservoir physical property, which can reduce the reservoir porosity by 23% on average. The cementation can make the reservoir physical properties become further worse while the dissolution can improve reservoir properties and increase the reservoir surface porosity by 0.7% on average. Besides that, the results indicate the diagenesis of Chang 63reservoir in Huaqing area mainly belongs to the late of A middle diagenesis and partly belongs to the early of B middle diagenesis.

Ordos basin; Huaqing area; Chang63reservoir; diagenesis; physical property

07 Sedimentary evolution of bioclastic dolostone and its distribution regularities in Bohai X oilfield

ZHANG Wen et al(Tianjin Branch Company, CNOOC, Tanggu, Tianjin 300452)

Since the property of clastic rock in the middle-deep strata in Bohai sea is poor, the lacustrine bio-carbonatite reservoirs with good property become the important oil and gas exploration target at present. Shahejie formation in Bohai X oilfield exactly belongs to this type of reservoir. Based on tectonic evolution background, through sedimentary facies and evolution analysis, it is considered that the bioclastic dolostone layer in this kind of reservoir experienced four stages, which can be identified as the early, the middle, the late stage of S1 lower sub-member, and the early stage of S1 upper sub-member. Combined with drilling data analysis, it is believed the development of the bioclastic dolostone layer is controlled by ancient landform, the layer usually distributed in the slope zone, the superposition thickness of multi period biodetritus beach was large, presenting lenticular distribution on the section. By establishing the theoretical model, combining with the drilling data, the scope and thickness for the reservoir development are predicted, which is of guiding significance for oilfield development of this kind.

Key words:Bohai X oilfield; Shahejie formation; biodetritus beach facies; bioclastic dolostone; ancient landform; sedimentary evolution

12 Diagenesis and porosity evolution of Yingshan formation in Yubei area

LIN Xin(Research Institute of Exploration & Development, Northwest Oilfield Company, Sinopec, Urumqi, Xinjiang 830011)

Based on thin section, geochemical analysis, cathode luminescence and fluid inclusion, a detailed study of the diagenesis types and sequence of the lower-middle Ordovician Yingshan formation carbonate rocks and their relationships with porosity evolution in Yubei area was carried out. The results show the reservoir of the lower-middle Ordovician Yingshan formation in Yubei area is subjected to such diageneses as penecontemporaneous dolomitization, burial dolomitization, 3 phase dissolution, 3 phase cementation, filling, compaction and pressolution, among which the dolomitization and dissolution act as the significant effects on the reservoir. According to the order and porosity evolution characteristics in diagenesis, the diagenetic sequence and porosity evolution of Yingshan formation were summarized.

Key words:Yubei area; Yingshan formation; diagenesis; porosity evolution

22 Physical property characteristics and its influential factors of Leijia-Gaosheng area in western sag of Liaohe depression

ZHOU Xiaolong(Research Institute of Exploration & Development, Liaohe Oilfield Company, PetroChina, Panjin, Liaoning 124000)

Based on physical properties of crude oil and related geological background, the crude oil of Leijia-Gaosheng area in western sag of Liaohe depression could be classified into extra-heavy oil, heavy oil, medium oil and light oil. At present the region mainly generate immature oil, with heavy quality and thick viscosity. With the increase of buried depth, the crude oil physical property is changing in a good trend. Horizontally, from south to north, the relative density change from light to heavy. The controlling factors of oil property are more complex. The internal cause is mainly for oil source differences, which includes parent rock types, source rock maturity and formed sedimentary environment. While the external cause is mainly by the external environment of crude oil to its secondary transformation in the process of oil and gas accumulation and late preservation, which includes oil and gas migration, fault activities, secondary changes and oilfield development.

Key words:western sag in Liaohe depression; physical properties of crude oil; distribution regularity; influential factors

30 Provenance and sandstone distribution regularity of upper sand formation from Ek22 reservoir in Kongxi slope

LIN Ling et al ((Research Institute of Exploration & Development, Dagang Oilfield Company, PetroChina,Tianjin 300280)

Ek22 member is the main oil-bearing strata in Kongxi slope because of its shallow buried depth, stable distribution and wide oil-bearing area. In order to carry out an in-depth study on provenance scope, sand body scale and distribution regularities, the oil groups of Ek22 reservoir in Kongxi slope were divided into the upper set and the lower set, and the upper set was considered to be the study target. Based on characteristics of light and heavy minerals, sand body distribution regularities and seismic reflection characteristics, a systematic study on the influencing factors which affected the provenance location was carried out. The results indicate the detritus in the study area are believed to come mainly from the Xuyangqiao, Kongdian, Cangshi, Shenvsi and Yesanbo.

Key words:Kongxi slope; Ek22 Formation; provenance system; sandstone distribution

34 Diagenetic evolution and pore characteristics of Chang 6 reservoir in R area of Ordos Basin

ZHAO Dong et al (State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an, Shaanxi 710069)

By using cathode-luminescence, SEM, x-ray diffraction, casting thin section and intrusive mercury, the diagenetic evolution sequence, stage and micro-pore characteristics of Chang 6 reservoir in R area of Ordos Basin was discussed. The results show the main lithology is feldspathic sandstone and it mainly experienced compaction, cementation and dissolution. The cementation made an obvious damage on reservoir property, which was the main reason for reservoir density. Combined with sedimentary environment and pore characteristics, digenesis was divided into 5 diagenetic facies. Primary and secondary pore were mixedly developed, the average porosity is 6.71% and average permeability is 0.46 ×10-3μm2. This reservoir has strong heterogeneity and it belongs to low porosity and low permeability. In process of pore evolution, mechanical compaction and cementation play a destructive role in reservoir physical properties, while the solution can improve the physical properties.

Key words:Ordos Basin; Chang 6 reservoir; diagenesis evolution; diagenetic facies; pore characteristics

39 Different types of diagenetic facies and its micro seepage characteristics of Chang 6 reservoir in Jiyuan area

ZHAO Yu et al (State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an, Shaanxi 710069)

Chang 6 reservoir in Jiyuan area of Ordos Basin belongs to low porosity, low and ultra-low permeability. Based on SEM, cast sheet, X-diffraction and flooding experiments of real sandstone microscopic model, the study on diagenetic facies and micro seepage characteristics of Chang 6 reservoir was carried out. The results show there were significant differences of flow characteristics between different types of diagenetic facies. By using comprehensive analysis of experimental results of real sandstone microscopic model displacement , the chlorite cementation residual intergranular pores diagenetic facies is the most favorable diagenetic facies and feldspar dissolution followed.

Key words:Jiyuan area; Yanchang Formation; Chang 6 reservoir; diagenetic facies; micro seepage characteristics;

72 Macroscopic heterogeneity of the Yan 10 reservoir in Beisan area, Maling oilfield

SANG Yu et al (State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an, Shaanxi 710069)

In Yan 10 reservoir from Beisan area of Maling oilfield, parallel bedding, cross bedding and oblique bedding were mainly developed and the multi periods positive rhythm superposition was the main characteristics. From top to bottom, the sedimentary facies were from meandering to braided river facies transition, and the reservoir heterogeneity was enhanced. It was predicted the braided river changed more frequently than meandering river and the deposition was more complicated. Laterally, the heterogeneity degree in the study area was strong, which would greatly affect the actual production of oilfield.

Key words:Maling oilfield; Yan 10 reservoir; sedimentary microfacies; heterogeneity

84 Genetic analysis and identification methods of Chang 61 low-resistivity oil layer in Fanchuan area

LI Kang et al(Research Institute of Shaanxi Yanchang Petroleum (Group) Co.，Ltd.，Xi'an Shaanxi 710075)

Chang 61 reservoir of Fanchuan area generally belonged to low resistivity reservoir, which made it difficult in oil layers' identification. By contrasting laboratory tests and production data, combined with geological characteristics of Chang 61reservoir, by means of the methods of cross-plot and natural potential overlaps, the genetic analysis of low resistivity was carried out. The results indicated the complicated pore structure of Chang 61led to higher irreducible water saturation and higher formation water salinity, and the increased conductivity of clay minerals was the main reason of low resistivity. It was concluded the methods of cross-plot method and natural potential overlaps could effectively identify the low resistivity reservoir.

Key words:Fanchuan area；low-resistivity oil layer；Chang 61oil reservoir；genetic analysis；identification method

88 Reservoir sensitivity of Cenozoic tight sandstone reservoir in Lenghu area, northern margin of Qaidam Basin

WANG YanZhi et al (Research Institute of Exploration & Development, Qinghai Oilfield Company, PetroChina , Dunhuang, Gansu 736202)

To improve production capacity and reduce sandstone reservoir damage in the process of oil and gas exploration in Lenghu area, northern margin of Qaidam Basin, through core flow experiment, the sensitivity characteristics of tight reservoir was studied, and the quantitative evaluation of the reservoir sensitivity was made. The experimental results show the reservoir had strong velocity sensitivity, strong water sensitivity and strong salt sensitivity, while the alkali sensitivity damage changed greatly, from non-alkali sensitive to strong alkali sensitivity and weak acid sensitivity. The sensitivity study provided a good guiding significance for oil and gas exploration and reservoir protection in this area．

Key words: Lenghu area; Cenozoic; reservoir sensitivity; tight sandstone

96 Reservoir architecture and remaining oil enrichment pattern of braided river——A case study from Huanjiang oilfield in Ordos Basin

HUANG Lisha et al(Department of Resources and Environment, Yangtze University, Wuhan, Hubei 430100)

In view of the problems of Huanjiang area, such as high waterflooding control degree, complicated remaining oil distribution and great tapping difficulty, by taking full consideration of sedimentary regularity of sand body in braided river reservoir, the reservoir internal architecture was studied. Based on reservoir architecture division scheme that advised by Miall in early years, level-5 classification scheme of reservoir architecture for braided river was proposed. Combined with coring and logging data, the sand bodies of braided channel and beach dam were identified and classified. At the same time, the space combination style and superimposed relationship were discussed. In the end, 8 kinds of remaining oil enrichment patterns corresponding to different configuration unit combinations were proposed. Therefore, the theory of clastic rock reservoir architecture in Huanjiang area was deepened, which provided a good guidance for secondary development in the study area.

Key words:Huanjiang oilfield; braided river; reservoir architecture; remaining oil enrichment pattern

100 Differentiation deep profile control in extra high water cut stage

SHI Shubin et al (Shengli Oilfield Company, Sinopec, Dongying, Shandong 257000)

In view of the poor effect of traditional profile control technology in high water cut stage, the profile control mechanism of different water cut stages was studied. By using numerical simulation, the waterflooding levels of reservoir in high water cut stage were classified, the corresponding technical countermeasures for different waterflooding levels were developed. The results indicate the profile control effect was the joint effect of swept volume expansion and pressure gradient fluctuation. In medium-high water cut stage, it was effective with long duration, while in extra high water cut stage, it was effective with long duration, which was mainly caused by the role of pressure gradient fluctuation. High strength plugging agent governance extra high water flooding area was the foundation to improve the oil recovery, high strength mobility regulatory governance high water flooding area was the key, and relative permeability modifier governance medium water flooding area was the core.

Key words:extra high water cut stage; deep profile control; numerical simulation; technical countermeasures

104 Optimization and application of perforation scheme in light oil reservoirs of Bohai oilfield

WU Xiaozhang et al(Tianjin Branch Company, CNOOC, Tanggu, Tianjin 300452)

In consideration of bottom water coning and bad development effectiveness because of inappropriate thickness of unperforated intervals of light oil reservoirs in Bohai oilfield with active edge and bottom water, by using numerical simulation method, the effects of the horizontal distance between the production well and inner oil boundary, the vertical distance between the bottom of oil layers and oil-water contact, oil layer thickness, oil viscosity, permeability contrast on the thickness of unperforated interval were analyzed. The results show the thickness of unperforated interval increased as the viscosity increased, and the unperforated interval was unnecessary when the distance between the production well and inner oil boundary was over 100 meters for light oil reservoirs in Bohai oilfield. The optimum thickness of unperforated interval was found to be 3 meters when the oil viscosity was less than 5 mPa·s. Perforation scheme template of light oil reservoirs in Bohai oilfield was established at the first time, which provided good guidance for rational development of similar oilfields.

Key words:perforation scheme; thickness of unperforated interval; permeability contrast; medium-light oil reservoirs; Bohai oilfield

115 Exploration and practice of air drilling technology in Karst area

LI Qing et al(Southwest Branch Company, Shengli Petroleum Engineering Co., Ltd, Sinopec, Deyang, Sichuan 618000)

With the deep exploration and exploitation of petroleum and natural gas, the ancient Karst was found to be a good storage structure for oil and gas. However, the drilling engineering in karst area had to face tremendous challenges due to unique geological characteristics. Based on geological features of Karst, the formation principle of Karst was briefly introduced, the drilling difficulties and risks were analyzed, and then measurements for coping with caves and underground river were proposed. The greatest advantage of air drilling technology was applied to deal with the malignant cave leakage in Karst area, which achieved faster and safer drilling. Anye 1 was a parameter well located in the typical Karst area. The application of air drilling was successfully solved the challenges caused by underground river. At the same time, it obtained high ROP and shortened the drilling cycle in Anye 1. The results indicated that the air drilling technology provided good guidance for drilling in Karst area.

Key words:Karst; lost circulation；drilling；air drilling technology

118 Design optimization of sidetracking horizontal well parameters in extra-high water sandstone mature oilfield

LI Yanan(Research Institute of Exploration & Development, Liaohe Oilfield Company, PetroChina, Panjin, Liaoning 124010)

K oilfield of Kazakhstan is a medium-high porosity and medium-high permeability layered sandstone oilfield with complex reservoir lithology and strong Interlayer heterogeneity. It has been exploited by inverted nine spot water flooding pattern for 37 years. By the end of September 2015, the comprehensive water content of K oilfield has reached 90.1% and been in high water stage. The drilling of K2357C well that is the first sidetrack horizontal well of K oilfield was finished at the end of 2010, which was the prelude for large scale implementation of sidetracking horizontal well. To study and evaluate the potential, by applying the theory of geology, well logging and reservoir engineering, the low productive and inefficient wells were selected, the layers were optimized, a reasonable length of horizontal section was demonstrated, the vertical position of the horizontal segment and a reasonable amount of fluid production were analyzed. After deploying 45 sidetrack horizontal wells, the daily oil production of single well and water cut were superior to that of straight wells at the same period, which proved the feasibility of sidetracking horizontal wells in extra-high water sandstone mature oilfield.

Key words:Kazakhstan; sandstone oilfield; waterflooding development; design optimization

124 Design and application of concentric double-tube hydraulic pump sand carrying oil production diagnosis and optimal design system

CHEN Rui (Oil Production Technology Institute of Dagang Oilfield Company, PetroChina, Tianjin 300280)

To improve the rationality of concentric double-tube hydraulic pump sand carrying oil production project design, to prevent sand deposition and improve development efficiency, concentric double-tube hydraulic pump sand carrying oil production diagnosis and optimal design system were discussed, whichcould realize condition diagnosis and optimal design through deal with production data and process design data. The technological process and the key technology of concentric double-tube hydraulic pump sand carrying oil production diagnosis and optimal design system were mainly described in Kongdian oilfield. The application results showed that the system could realize condition diagnosis and process parameters optimal design.

Key words:concentric double-tube; hydraulic pump; sand carrying oil production; working condition diagnosis; optimal design; Kongdian oilfield