The Reservoir Of Shanxi-2 Formation Expansion Potential Evaluation And Screen Of Favorable Area In Zizhou Gasfield

The wellhead pressure of earlier production of Zizhou gasfield declines quickly, inefficient wells increase. This poses challenges to stable the production.The comprehensive utilization of logging data, core observation, and a large number of laboratory testing results,combining macroscopic with microcosmic, from qualitative analysis to quantitative evaluation, the system researched the gas field and its surrounding areas of structural feature,sedimentary microfacies,sand distribution characteristics,reservoir characteristics and diagenesis.On the basis of them,performing the evaluation of the potential edge extension,and screening the favorable target area.(1)The structure of the study area basically inherited the overall characteristics of Ordos Basin regional structure,developing many different sizes of the nose structure from north to south. Those nose structure mainly distributed in surrounding areas such as tai 8 well, yu143 well, yu 39 wells,and the nose structure has a good inheritance.(2) Reservoir of Shanxi- 23 formation in the study area mainly developed delta plain deposition, it developed underwater distributary channel on the plane,and many fluvial channel intersected in the centre of gas field. In vertical, reservoir developed many times of fluvial channel and superimposed each other. Reservoir of Shanxi- 23 formation in the study area of sand body developed from south to north trending,and distributed thick clumps or vertical superimposed types.And the reservoir sand body have a good connectivity in horizontal, single-layer thickness ranging from 2.5 to 6 meters, the largest is almost 10 meters.(3)Reservoir of Shanxi- 23 formation in the study area of lithologic character is mainly composed of quartz sandstone.The types of pore include residual intergranular pore, dissolved pores and intercrystal micropore.The assembly types of pore are mainly intergranular pore-solution pore type.Throat types are mainly variable section of contraction part, the second is flaky or curved lamellar throat.With reference to many indicators,they can be divided into 6 types of diagenetic facies, kaolinite and quartz increased cementation weak solution facies is most widely distributed.(4)According to the above analysis result, reservoir of Shanxi- 23 formation in the study area can be divided into four categories I, II, III and IV. On the basis of the reservoir evaluation,we establish favorable zone optimization criteria of the main layer series of Shanxi- 23 formation,and screening out the favorable area of class I and class II reservoir,providing the basis for further exploration and development in Zizhou gasfield.