ABSTRACTS

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Vol.31 No.6, Nov.2017

01 Strike-slip structure characteristics and genesis analysis of A tectonic, south of Liaozhong sag in the Liaodong bay depression

LIU Feng et al (Tianjin Branch of CNOOC China Ltd., Tianjin 300452)

Based on 3D seismic data interpretation results, two main strike-slip faults in A tectonic, south of the Liaozhong sag in the Liaodong bay depression were identified. Under the control of the diversity of its developmental characteristics, different kinds of associated tectonic were formed. Combined with the physical simulation experiment, the tectonic causes were analyzed. The results indicated the clear existence of strike-slip faults and its associated tectonic formed by the petroleum geological significance and two major strike-slip faults on both sides because of the difference of stress conditions and activity in different positions, strike-slip faults and their associated fault formed multi-stage‘Y’, negative flower structure and shovel type negative flower structure three types of tectonic style, and accordingly formed strike-slip double stretch superposition structure, strike-slip master fault extensional structure and strike-slip fault in extrusion structure control three structure types, with different trap effect and hydrocarbon migration conditions.

Liaozhong sag; strike-slip fault; fracture characteristics; structure characteristics

12 Sedimentary characteristic of Chang 8 oil reservoir in the Shui Mogou area, Ordos basin

LIANG Weiwei et al (Research Institute of Shannxi Yanchang Petroleum(Group) Co.Ltd., Xi’an, Shaanxi,710075)

Chang 8 oil reservoir in the Shui Mogou area of Fuxian county, Ordos basin is mainly composed of fine sandstone and powder-fine sandstone, which is medium in roundness and porosity, with medium structure maturity. The main sedimentary background of Chang 8 oil reservoir is lacustrine delta sedimentary system, which can be subdivided into subfacies of predelta and delta front. On this basis, three kinds of microfacies were mainly developed, namely underwater distributary channel, subaqueous diversion channel and the former deltaic mud. The main layer is 821, which is in the leading edge of the delta, and the large-scale development of underwater distributary channel sand body is the main oil and gas reservoir, and the reservoir is mainly controlled by sedimentary facies.

Key words: Ordos basin; Chang 8 oil reservoir; sedimentary microfacies; sand body distribution

15 Tectonic characteristics and trap styles in northern sag of northern depression in the south of Yellow Sea basin

REN Yan et al (Shanghai Branch of CNOOC Ltd.,Shanghai, 20030)

Because of complicated development conditions of all level of faults and big difficulty in tectonic evolution research, there had no commercial quantitative petroleum found in northern sag of northern depression in the south of Yellow Sea basin up to now. Based on fine structure interpretation of 3D seismic data of the northern sag, a research on both tectonic characteristics and trap styles in the northern sag was carried out, which is a prospect zone for petroleum exploration. The results indicate the faults evolution in this area can be divided into 4 stages,namely, the early stage, the middle stage, the late stage and the stage of sustained developing. There are distinct structure differences between the upper strata and the middle-down strata, the shape of middle-down strata varies intensely but the upper strata change gently. The main tectonic style of northern sag included graben, horst,fault terrace, flower structure and flower-liking structure.The north sag was controlled by the regional extension and strike-slipping, and in terms of trap styles, fault noses and fault blocks are the main styles developed in this place, and then tectonic-lithologic trap, which blocked by faults. Generally, the planar feature of trap styles in this area was characterized by zone.

Key words: south Yellow Sea basin; northern sag area; fracture active stage; tectonic characteristics; trap styles

20 Genesis of thick dolomite in the lower Ordovician Ma 55in eastern area of the Sulige gas field

WANG Yanliang et al (No.5 Gas Plant of Changqing Oilfield Branch Company, CNPC, Xi’an, Shaanxi,710000)

Dolomite reservoirs in M55of lower Ordovician in eastern area of the Sulige gas field is characterized by big thickness of single well, quick pinching out in horizontal direction, which is distinctively different from the characteristics of dolomites reservoir in M51-4with thinner individual layer and good horizontal continuance in the Jingbian gas field. The reservoir lithology of this area is mainly of fine medium dolomite and fine powder crystal dolomite, which is the result of the combination of evaporation pump dolomization, reflux permeation dolomitization and deep-burial dolomitization. The dolomite types are mainly of fine or medium dolomites and fine or silty crystal dolomite, the pore types are mainly intercrystal pore and intercrystal dissolved pore. Through the research of petrology, geochemistry and diagenesis, the genesis of dolomite reservoir in this area was studied. The grain bank deposition is an important condition for the formation of favorable reservoirs, the burial dolomitization is a precondition, and the burial phase dissolution is a key factor for reservoir formation.

Key words: Sulige gas field; lower Ordovician; dolomite reservoir; grain bank deposition

26 Reservoir characteristics and the influencing factors of physical properties of Chang 6 reservoirs in Wuding area, Ordos Basin

MENG Ziyuan et al (State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an, Shaanxi 710069)

By using casting thin sections, scanning electron microscopy (SEM), high pressure mercury injection, X-ray diffraction and other experiment testing methods, the physical properties study of Chang 6 reservoirs in Wuding area, Ordos basin was carried out, and the deposition and diagenetic effects on physical development were analyzed.The results indicate the lithology of the study area is mainly of gray fine arkose sandstone, the reservoir space types are mainly of original intergranular pores and dissolved feldspar pores, and the reservoirs can be divided into three parts based on capillary pressure curve,namely dissolved-intergranular pore, dissolved pore and intergranular micropore. Porosity and permeability are positively correlated, and the porosity and permeability of different pore types have obvious different zoning. Sedimentation and diagenesis jointly affect the evolution of reservoir properties, the effect of sedimentation on reservoir physical properties is mainly due to the muddy content. Compaction has a negative correlation with porosity and the cementation has a good effect on the physical properties. The dissolution effect in the study area is not obvious, which has little effect on the physical properties.

Key words: Ordos basin; Chang 6 reservoirs; diagenesis; reservoir characteristics

31 Reservoir characteristics of Yan 9 member of the Yan’an formation in the north of Zhiluo oilfield

LIU Feifei (School of Earth Science and Engineering of Xi’an Petroleum University, Xi’an, Shaanxi 710065)

By using experimental testing techniques such as core observation, rock slices identification, scanning electron microscopy and pressure mercury test, the characteristics and heterogeneity in Yan’an reservoir was studied. The results indicate the rock types of the Yan 9 member are mainly gray, gray-green, gray-brown feldspar lithic quartz sandstone, the sorting of sandstone is medium-good, roundness is mostly round, secondary edge-sub-round. Particles are between the line, pointline contact, point contact and bump contact can be partially seen, mostly for particle support. From the capillary pressure curve, it can be seen: the pore type of Yan 9 is medium hole-throat type, medium and small hole type.The reservoir types in Yan’an formation include the following four types, namely intergranular dissolution, intergranular dissolution, residual intergranular pores and casting holes. Among them, 79.23% of the intergranular pores are the largest, 0.63% of the casting holes is the least. The reservoir of Yan 9 member belongs to medium porosity, medium-low permeability reservoirs, and the reservoirs have good physical properties.

Key words: Zhiluo oilfield; Yan’an formation; reservoir characteristics; pore microcosmic characteristics

36 Log facies types of tight sandstone reservoir in the Daniudi gas field

GAO Qingsong et al (Exploration & Development Research Institute, North China Oil and Gas Branch, Sinopec, Zhengzhou, Henan 450006)

Daniudi gas field is located in the north of Ordos Yishan slope of the basin, the main gas bearing strata are the upper Paleozoic Carboniferous Taiyuan formation,Permian Shanxi formation and Shihezi formation, which belongs to tight sandstone reservoir. Daniudi gas field mainly experienced the transgression in late Carboniferous, regression in early Permian transgressive delta in Shanxi period, sea-land transitional fluvial deposits in lower Shihezi formation and there formed various log facies types. By using natural gamma curve, the reservoir can be divided into eight rock types, the reservoir and favorable sedimentary facies under different sedimentary systems were made clear. He3, He2and He1of Shihezi formation are mainly of braided fluvial facies deposit and the favorable facies belt is braided river main channel. Shan2and Shan1 of Shanxi formation are mainly of delta plain sedimentary and the favorable facies belt is distributary channel. Tai2of Taiyuan formation is mainly of barrier island-lagoon deposits and the favorable microfacies is barrier bar.

Key words: Daniudi gas field; tight sandstone; reservoir logging facies

41 Diagenesis and porosity evolution of the reservoirs from the upper Triassic in the Yichuan basin

HOU Juan et al (Exploration＆Development Research Institute of Henan Oilfield Branch Company, Sinopec, Nanyang, Henan 473132)

The formation of the upper Triassic sandstone in the Yichuan basin is dense and the heterogeneity is strong.Due to unclear understanding of diagenesis and its pore evolution, the hydrocarbon deployment was restricted to some extent. Through thin section, scanning electron microscopy (SEM) and X-ray analysis of the results of research, combined with the burial history, thermal history and other information, the Triassic reservoirs of Yichuan basin are mainly of fine sandstone and feldspar lithic sandstone, with poor physical properties in general, which belongs to low porosity and low permeability sandstone reservoir. Diagenesis of upper Triassic belongs to stage A of middle diagenesis phase. The early diagenetic compaction and cementation are main factors to decreasing porosity of reservoir. The formation of secondary porosity in feldspar corrosion has obvious effect on sandstone reservoir performance. The early diagenesis reservoir has been densified before oil and gas filling.

Key words: Yichuan basin; upper Triassic; diagenesis; porosity evolution

56 Karst zone structure and reservoir models of Ordovician buried hill, Caofeidian oilfield in the Nanpu depression

ZHANG Wen et al (Tianjin Branch of CNOOC(China) co., LTD., Tanggu, Tianjin 300459)

Ordovician buried hill experienced a long geology rebuild after the post-deposition in the southwest of the Nanpu depression. Its karst zone structure and characteristics of reservoir distribution are different from the surrounding buried hill reservoir. Affected by the cementation, the buried hill karst zone of this area does not have the complete model of carbonate karst. According to the drilling, core, logging, DST information and laboratory analysis data, karstification of this area develops in three layers of aplite-dolomite controlled by lithology. The karst reservoir type is layered lithologic-structural reservoir. The reserving space mainly includes pores, caves and cracks, which belongs to low porosity and low permeability reservoirs. The reservoir type of karst zone is stratified lithology-structure reservoir.

Key words: Nanpu depression; Ordovician; carbonate buried hill; karst zone structure; reservoir distribution

61 Discussion of Ordovician carbonate reservoirs in the Hadexun oilfield

CHEN Xin et al (Petroleum Engineering School,Xi’an Petroleum University, Xi’an, Shaanxi 710000)

Fractured vuggy carbonate reservoirs in Hadexun oilfield have complex geological features and the reservoirs are complex and diverse. In early stage of oilfield development, because the data of drilling density and pressure between wells is missing, the understanding of reservoirs have certain restriction, to determine the types of reservoir as soon as possible and prepare for the development of countermeasures in advance. By using static seismic data, well logging, dynamic data of the production characteristics, the type of energy drive, the pressure recovery curve, there are mainly two reservoir types, namely the constant volume reservoirs and multi fracture cave and connectivity reservoir. The characteristics and characteristics of these two kinds of oil reservoirs are separately analyzed. There are obvious differences between the two types, and therefore different development strategies should be adopted.

Key words: Hadexun oilfield; carbonate rock; connectivity; reservoir types

69 Reservoir architectures and the impact on remaining oil distribution of delta front

—A case study on Baibao oilfield in Ordos basin

DAI Tingting et al (Department of Resources and Environment, Yangtze University, Wuhan, Hubei 430100)

In order to explore delta front reservoir architecture features and the remaining oil distribution, due to the strong reservoir heterogeneity and the complex characteristics of remaining oil distribution on Bai 157 well block of Baibao oilfield in Ordos basin, by making full use of cores, well logging and production data, thorough the research on the reservoir internal architecture, the types and characteristics of delta front reservoir architecture elements were clearly introduced. Boundaries of a single sand body has four recognition methods and the superimposed pattern on the vertical and lateral configuration elements were put forward. In vertical direction, it was mainly divided into erosion type, overlapping and isolation type. In side direction, it could be divided into two types, namely lateral tangential type and lateral separated type. The residual oil enrichment of different configurational elements was different, and there were three models of distribution of remaining oil in anti-metrical estuarine dike body, top, middle and bottom models. While in the normal rhythm of the underwater distributary channel, the remaining oil was generally concentrated in the upper part of the middle.

Key words: Ordos basin; Baibao oilfield; delta front;reservoir architecture; remaining oil distribution

74 Uncertainty analysis of geological reserves based on 3D geological model

——A case study on P reservoir in Niger delta basin in the west Africa

WANG Tong et al (Petroleum Exploration & Development Research Institute of Sinopec, Beijing 100083)

In order to properly evaluate the oil and gas volumes in place, the reasons for volume uncertainty are demonstrated. The technical limitation, data limitation and subjectively parameters selection listed as the main causes of volume uncertainty. Uncertainty analysis based on 3D geological modelling are studied due to the uncertainty in the input data and inconsistency between them. The volume uncertainty analysis workflow is established and the geological parameters affecting volumes are summarized as top surface, sand distribution, fluid contacts, porosity,water saturation and volume factor based on the study in an oilfield of Niger delta basin. By taking P reservoir of Niger delta basin in west Africa as an example, the system analysis of the geological reserves evaluation of oil and gas reservoirs of the uncertainty of the geological factors is carried out, which points out the top surface structure and sand body distribution, fluid interface, reservoir parameters are the main factors affecting geological reserves calculation results. Uncertainty analysis of oil and gas volumes in place by using 3D geological modeling method properly indicates the risks in volume estimation, which provides the basis for scientific decision in investment,well placement and production planning.

Key words: Niger delta; geological reserve assessment; 3D geological model; probabilistic method, volumetric method

98 Matching technology for increasing ROP in tight oil horizontal well in Placanticline and Qijia of the Daqing oilfield

CHANG Lei (Production Engineering Research Institute of Daqing Oilfield co., LTD, Daqing, Heilongjiang 163453)

To address problems such as long horizontal section,low ROP, high drilling construction difficulty, long drilling cycle, hole instability in tight oil horizontal well in Placanticline and Qijia areas of Daqing oilfield, with well trajectory optimization, the drilling construction difficulty was declined. Through optimized high efficient screw, the drilling construction efficiency was improved. With the development and application for increased ROP drilling tools, the ROP was increased highly in deflecting section and horizontal section. With the development of high performance water-based drilling fluid system, the antisloughing in long horizonal section was achieved. The ROP increased highly by 14 wells field experiment. The ROP was 10.53 m/h, which increased 25.68% by contrast before the experiment. Form the matching technology for increasing ROP in tight oil horizontal well in Placanticline and Qijia areas of Daqing oilfield.

Key words: Daqing oilfield; tight oil; horizontal well;drilling technique; friction torque

112 Experimental study of chromium-gel flooding system

LI Guifeng (No.2 Oil Production Plant of Zhongyuan Oilfield Company, Sinopec, Fanxian, Henan 457532)

In view of oil reservoir heterogeneity, the study of chromium gel flooding system was carried out. The results indicated with the increase of polymer concentration and the number of crosslinking agents, the gelling time decreased. With the increase of polymer concentration and crosslinking concentration, the gelling time and gelling strength rose. The gelling stability went up with the increase of polymer concentration, while increased first then declined later with the increase of the crosslinking agents and coagulants concentration. Performance evaluation results of the preferred gelling system indicated the gelling time and the gelling strength increased first then declined later as the mineralization degree increased. With the increase of pH, gelling time grew, and gel strength increased first then dropped later. The system was resistant to scour, the ultimate recovery improved 21.26% on the basis water flooding, and reflected good flooding effects in heterogeneity stratum.

Key words: chromium gel; system optimization; performance evaluation; recovery

119 Influence of testing time on core conductivity under different closing pressures

LIU Xiang et al (College of Energy Resources,Chengdu University of Technology, Chengdu, Sichuan 610059）

The influence of the testing time on the fracture conductivity was investigated by using the quasi-triaxial core holder to compress the fractured cores. The experimental results indicated with the increase of the testing time, the diversion ability gradually decreased, before 60 min it declined faster, after 60 min it declined slower. The error of curve fitting was relatively large, and the error decreased as the pressure time increased. By using the fitting formula, the conductivity of the pressure was predicted, and the workload of the experiment was reduced.When the cracks were at the closing stage, the rock was under compression, which was consistent with the actual situation of reservoir. The results at this stage could be used for diverting capacity of reservoir evaluation, which more truly reflected the condition of reservoir fracture diverting capacity and the relationship between the stress.

Key words：pressurizing time; closing pressure; flow conductivity; crack width