ABSTRACTS

Vol.31 No.3， May 2017

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Vol.31 No.3， May 2017

01 Depositional models of sand-rich sublacustrine fan and favorable exploration targets in Bohai oilfield

WANG Gaiwei et al (Bohai Petroleum Institute of Tianjin Branch Company, CNOOC, Tanggu, Tianjin, 300459)

Through systematic analysis on development characteristics of sublacustrine fans in Bohai oilfield, the sublacustrine fans of Bohai oilfield could be divided into two depositional models: one type was related to early inherited slope break belt and the other was related to synsedimentary slopebreak belt built by large delta construction. The sand-rich characteristics and the scale of these two types was compared and analyzed. By taking BZ21 area as an example, based on the analysis of palaeomorphologic patterns and synsedimentary slope break belt, by means of fine seismic tracing and composite microfacies features description, the depositional models of large-scale sublacustrine fan group in BZ21 area were established, which found sand-rich areas, described sad-rich boundaries and pointed out favorable subtle reservoir exploration targets of sublacustrine fan types in BZ21 and BZ19 areas.

Bohai oilfield; Paleogene system; sublacustrine fan; sedimentary model; exploration potential

15 Reservoir forming conditions of the third member of Funing formation in Qutang sub sag, Hai'an Sag in Subei Basin

ZHOU Tao (Exploration & Development Research Institute, East China Company, Sinopec, Nanjing, Jiangsu 210011)

Oil source of the third member of Paleogene Funing formation in Qutang sub Sag, Hai’an Sag in Subei basin was mainly from source rock of the second member of Funing formation. The effective source rock of the second member of Funing formation in the study area, which belonged to good source rock, with characteristics of favorable thickness, high abundance of organic matter, good type and mature evolution stage. Therefore, it provided sufficient oil source for reservoir of the third member of Funing formation in the study area. The third member of Funing formation widely developed sandstone, and it belonged to the middle porosity-low permeability reservoir, with favorable reservoir properties. Lacustrine mudstone of the fourth member of Funing formation was the regional seal of the third member of Funing formation, which had good seal ability and was beneficial for hydrocarbon preservation. The migration pathway of the third member of Funing formation was mainly faults and micro fractures which undercut to the second member of Funing formation. Oil and gas generating from the source rock of the second member of Funing formation in the drive under abnormal pressure migrated upward to the third member of Funing formation reservoir.

Key words:Subei basin; Hai'an sag; Qutang area; the 3rdmember of Funing formation; reservoir forming conditions

19 Shale gas accumulation conditions and exploration prospect in Niutitang Formation of lower Cambrian in southern Guizhou

WAN Meng et al (Key Laboratory of Karst Environment and Geological Hazard Prevention of Guizhou University, Guiyang, Guizhou 550025)

Shale gas is a state of adsorption, free, or dissolve occurrence in mud shale. It belongs to a kind of unconventional natural gas resource. The sedimentary environment gets deeper from the north west to south east in Niutitang Formation of lower Cambrian in southern Guizhou. Profitable sedimentary phase of shale gas is for deep sea shelf - deep sea basin. By means of profile and well testing, the kerogen type of Niutitang Formation has the feature of typeⅠ. Higher organic carbon content, higher thermal evolution degree, lower permeability and developed micro-fracture have good material basis for shale gas reservoirs. Through analysis of evaluation parameters, three areas were optimized for shale gas exploration.

Key words:lower Cambrian in southern Guizhou; Niutitang Formation; shale gas; accumulation condition

26 Sedimentary microfacies of fan delta in deep strata series of Anpeng oilfield

HUANG Lei et al (Exploration & Development Research Institute of Henan Oilfield Company, Sinopec, Zhengzhou, Henan 450018)

Through a lot of core observation and description, combining with the sedimentary characteristics, logging data and regional geological data, the comprehensive analysis of sedimentary characteristics and sedimentary facies in deep strata series of Anpeng oilfield was carried out. The results indicated the region belonged to fan delta sedimentary system and had 9 kinds of lithofacies. In sandstone and conglomerate, parallel bedding, oblique bedding and massive bedding were mainly developed. There mainly developed underwater distributary channel, mouth bar, sheet sand microfacies, etc. The sedimentary microfacies distribution characteristics of different sand bodies at different periods were made clear and compared with that of in alluvial fan sedimentary system. Based on forming conditions, lithologic features and sedimentary microfacies analysis of fan delta, the study on identification mark of the fan delta was carried out and its sedimentary model was established.

Key words:Biyang sag; Anpeng oilfield；fan delta; sedimentary microfacies; sedimentary models

30 Sedimentary characteristics and geological implication of Chang-9 reservoir in northwest of Ordos basin

LI Jihong et al (Exploration & Development Research Institute of Changqing Oilfieid Company, CNPC, Xi'an, Shaanxi 710018)

According to cores, logging and testing analysis, the sedimentary characteristics of Chang-9 reservoir in northwest region of Ordos basin were studied. The results indicated it wholly belonged to marsh environment and mainly developed braid-river delta plain subfacies. The sedimentation was controlled by two provenance systems in northwest and northeast, especially the northwest provenance. The petrographic study showed the sandstone in Chang-9 reservoir were mainly of arkose and lithicarkose with low compositional maturity and moderate structural maturity. Affected by the sedimentation, the sand body of Chang-9 reservoir was vertically characterized by uniform type without graded change and composite graded type. The main reservoir body was of distributary channel microfacies and it was good for oil accumulation.

Key words:Ordos basin; braided river delta salt; sedimentary facies; sand body structure

38 Favorable petroleum exploration prospects in Bole basin

ZHANG Mei (West Branch, Exploration & Development Research Institute of Shengli Oilfield Company, Sinopec, Dongying, Shandong 257000)

The hydrocarbon exploration in Bole basin has not made major progress at present and then systematic analysis of hydrocarbon prospects was needed. Combined with the methods of field survey, geochemical analysis and seismic data, the evaluation on petroleum geological conditions of Bole basin was carried out. The results indicated there were three sets of source rocks in Bole basin, among which the Permian hydrocarbon source rock was the main one, there were 5 sets of reservoir-caprock assemblages, the Carboniferous marine carbonate rocks, clastic rocks and Paleogene fluvial facies sandstone were favorable reservoirs, the structural traps were mainly controlled by thrust faults and the area in southwest of Jinghe depression was the most favorable petroleum exploration prospect.

Key words: Bole basin; source rock; reservoir; trap; favorable petroleum exploration prospects

48 Genetic model and exploration potential of beach-bar sand in Sishilicheng slope belt of Yanqi basin

JIN Yunyun (Exploration & Development Research Institute of Henan Oilfield Company, Zhengzhou, Henan 450018)

The beach-bar sand depositional assemblage was identified from Badaowan formation in Sishilicheng slope belt of Yanqi basin. These sand bodies were coexisted with effective source rocks and had characteristics of good reservoir properties and good source-reservoir-caprock assemblage, which was good for lithologic reservoir accumulation. Little affected by late tectonic movement and destruction, the conservation conditions in the late stage were good. The comprehensive exploration of the beach-bar sand bodies was expected to open a new exploration area in Yanqi basin. The research results indicated in addition to adequate sediment provenance, the good hydrodynamic conditions and the suitable paleogeomorphic environment, the development of the beach-bar sand bodies in study area was also closely related to the development of the slope break belt and the forced regression.

Key words:Yanqi basin; beach-bar sand bodies; slope belt; genetic model; exploration potential

62 Application of S-wave velocity forward in Turbidity reservoir prediction of Dongpu sag

FAN Lingxiao et al (Exploration & Development Research Institute of Zhongyuan Oilfield Company, Zhengzhou, Henan 450000)

Turbidity sand bodies of the 3rdmember from Shahejie formation of ShaPuwei sub-sag, Dongpu sag were characterized by fast lateral variation, deep buried depth, thin thickness, strong diagenesis and strong concealing property. By using traditional wave impedance inversion, effective reservoirs and the fluid properties were difficult to be identified. Combined with logging data in Pu-138 block, based on rock physics theory, by using conventional logging data, multiple mineral components were obtained. According to Xu-White model and Biot-Gassmann equation, the shear velocity forward was obtained and the quantitative interpretation template was established. The prediction and inversion of turbidite sand reservoirs in Puwei area were carried out by using elastic parameters, the inversion results were consistent with the actual drilling results and the consistent rate reached 76%, which proved the effectiveness of this prediction method.

Key words:Dongpu sag; Turbidity sand body; S-wave velocity forward; reservoir prediction

66 Fracture prediction modeling of reef limestone reservoirs in south China Sea

ZHNAG Yongjiang et al (Shenzhen Branch, CNOOC Ltd. Shenzhen, Guangdong 518000)

Liuhua oilfield was a deep-water reef limestone heavy oilfield in south China Sea and had characteristics of complicated sediment environment, big structure uncertainty, big difficulty in reservoir property evaluation, strong anisotropy, developed fractures and dual porosity media. In order to make a study on distribution characteristics of reservoir fractures, based on depositional evolution of reef limestone and facies classification, by fully using coring, seismic, drilling and imaging logging, the fracture network model of the reef limestone reservoirs was established. The results indicated pressolution and dissolution seams with low angle and bigger crack opening were mainly developed in reef facies, while group seams with high angle were developed in beach facies, which was focused on the tectonic joints and tectonic soluble seams, with superiority striking in north west-south east. The influencing factors of the reef limestone fracture development in Liuhua oilfield included both the structural factors and the later diagenesis. The comparison between the research results and the dynamic status showed the method could provide good guidance for oilfield development.

Key words:Liuhua oilfield; reef limestone reservoir; stress field; imaging logging; fracture network model

73 Calculation methods of dynamic reserves of tight gas wells in Changqing oilfield

XIE Shan et al (National Engineering Laboratory for Low-Permeability Petroleum Exploration & Development, Xi'an, Shaanxi 710021)

Gas wells of Changqing oilfield were generally characterized by low permeability reservoirs, lack of pressure test data, unsteady working schedule and large amount of gas wells, the traditional appraising method was difficult to accurately evaluate dynamic reserves of gas wells in time. By considering characteristics of production and fluid mechanics in Changqing gas field, a practical dynamic reserves appraising method, which was based on superposition theory, was proposed. With merits of introducing superposition time into dynamic reserves equation of tight gas, this simplified method was useful to deal with variable rate without relying on typical curve fitting. Besides, the result of this method was correct and unique. Furthermore, a technical support was provided to realize quick estimation of dynamic reserves in Changqing gas field.

Key words:Changqing oilfield; tight gas reservoir; dynamic reserves; calculation method

84 Gas channeling and water flooding regularities of oil reservoirs with gas cap and edge water in JS oilfield of Bohai sea

CHENG Qi et al (Research Institute of Bohai Oilfield, Tianjin Branch Company, CNOOC, Tanggu, Tianjin 300452)

Shahejie formation of JS oilfield was a layered structure reservoir with gas cap, edge water and narrow oil rim. By adopting horizontal wells penetrating multiple layers, there was good effect in early development, while in late development gas channeling and water flooding occurred, which may lead to high output decline rate. Based on the study of sub-layer fine division and comparison, as well as sedimentary micro-facies, the combination models of major sandbodies were classified and the corresponding mechanism models were established. By using numerical simulation, the gas-oil-water three-phase migration regularity was studied and the characteristics of gas channeling and water flooding under different models were summarized. The research results successfully provided good guidance for treibgas and water plugging in many wells and realized good oil increasing effects.

Key words:2ndmember of Shahejie formation; JS oilfield in Bohai sea; combination model of sand body; gas channeling and water flooding

87 Well selection decision method of indepth profile control and displacement in offshore heavy oilfield

MENG Xianghai et al (Research Institute of Bohai Oilfield, Tianjin Branch Company, CNOOC, Tanggu, Tianjin 300452)

In offshore heavy oilfield, the commingled injection and production pattern with high strength will lead to the general development of preferential migration passage, and deep profile control is the key to realize the stable production of oil field. A well selection decision method of in-depth profile control and displacement which was suitable for offshore heavy oilfield was proposed. Starting from the static index, production performance index and dynamic monitoring index, through comprehensive screening, the evaluation index system of the selection well decision was established. Through membership function, the quantitative calculation of these indexes was realized. By using the fuzzy analytic hierarchy process, the index weight was determined step by step, and then the decision model of selecting well which could calculate the comprehensive evaluation factors was established. The field application results indicated the effect of increasing oil and decreasing water was good, the water decreased by 1.2%, the increased oil was of 6.10×104m3and the oil recovery increased by 0.21%, which fully proved the reliability of the method.

Key words:offshore heavy oilfield; deep profile control and displacement; selecting well index; fuzzy analytical hierarchy process

91 Remaining oil potential-tapping of offshore heavy oil reservoir at high water cut period--by taking CB oilfield in Bohai sea as an example

LIU Chunyan et al (Research Institute of Bohai Oilfield, Tianjin Branch Company, CNOOC, Tanggu, Tianjin 300452)

By taking heavy oil reservoir at high water cut period in CB oilfield, Bohai sea which only had one main production layer as an example, based on the combination of static and dynamic way of thinking, mathematical methods were used to analyze spectrum properties of logging curve and wavelet spectrum, high resolution sequence stratigraphic division and correlation technology of thick sand bodies were adopted to carry out subdivision. On the basis of sedimentary microfacies and reservoir heterogeneity, coupled with saturation logging data, based on the time shift saturation fitting method, remaining oil saturation of each layer and remaining reserves were described. The study results indicated it can successfully provide good guidance for horizontal well deployment of seven wells, the incremental oil effect was good and the expected increased oil recovery factor was 4.5%.

Key words:Bohai oilfield; high water cut period; remaining oil distribution

108 New progress on numerical simulation of volume fracturing in unconventional oil reservoirs

TANG Zichun et al (Petroleum Exploration & Development Research Institute, CNPC, Beijing 100083)

The efficient development of shale gas reservoirs was closely related to rational design of stimulated reservoir volume. On the basis of extensive literature research, a detailed overview of the numerical simulation techniques of volume fracturing in unconventional oil reservoirs was obtained. From the interaction between natural fractures and hydraulic fractures and the stress shadow and proppant simulation, the development of fracture mechanics model was described, and rhe principle of unconventional fracture model was introduced, which provided a good reference for further study. Besides the continuum medium model and discrete fracture network model in numerical simulation of volume fracturing in unconventional oil reservoirs were also described, the principles, ideas and applicability of numerical simulation were analyzed. Finally, the main direction of foreign research was summarized and further development of the numerical simulation for tight oil reservoirs in Changqing oilfield was put forward.

Key words:Changqing oilfield; unconventional reservoirs; numerical simulation; volume fracturing; discrete fracture network model

121 Experimental research and schematic design of surfactant system in ultra-low permeability reservoir of Dingbian oilfield

WANG Wei (Engineering Technology Research Institute, North China Branch of Oil and Gas, Sinopec, Zhengzhou, Henan 450006)

Aiming at the problems occurred in middle-late development period of low permeability reservoir in Dingbian oilfield, such as low oil displacement efficiency and poor development effect of water flooding, the research on surfactant oil displacement technology was carried out. Through indoor experiments, the HB-DB-1 surfactant system was selected out, which could enhance oil recovery rate of 11.1% under the conditions of 0.2% concentration and 0.3PV injection volume, and it could also reduce the displacement pressure. In the end the testing well group HK17A was optimized and the preparation of field test program was expected to improve the recovery rate by 2% ～ 3%.

Key words:Dingbian oilfield; ultra-low permeability reservoir; surfactant; displacement experiment; oil displacement efficiency