Study On Reservoir Characteristic Of The 8th Member Of Xiashihezi Formation And The First Member Of Shanxi Formation In The Northern Sulige Gas Field, Ordos Basin

the 8th member of xiashihezi formation and the first member of shanxi formation are the main gas-producing interval in the North Sulige gas field in Ordos Basin, it is vital significant to detailed research on its reservoir characteristics for the next exploration and development. The 8th member of xiashihezi formation and the first member of shanxi formation of north Sulige gas field in Ordos Basin are the main research object of this thesis. Based on predecessor's achievements, taking the theory of sedimentology and reservoir geology as a guide, by means of detailed observation and description of over 20 wells, analysis of quantity of thin section, cathodeluminescence, scanning electron microscope and date of mercury penetration, combined with analysis of logging, pore and permeability of core, diagenesis and reservoir characteristic of the 8th member of xiashihezi formation and the first member of shanxi formation of Sulige gas field were comprehensively researched, and several recognitions were obtained as follow.1. According to the clastic constituents statistics of 572 rock samples, using the principle of naming by triangle classification chart, in accordance with the difference of the clast (Q, F, R) constituents and content. The data points of He 8 member are mainly in area of quartz sandstone and debris quartz sandstone with the content of 19.74% and 68.75% separately, and the debris sandstone is relative few, which accounts for 12.41%. But the data points of Shan 1 member are mainly in area of debris quartz sandstone which accounts for 59.32%, and the secondly in area of l debris quartz sandstone which accounts for 34.46%, the quartz sandstone content was least, accounts for 6.22%.2. The study of the reservoir diagenesis showed that the destructive diagenesis of the sandstone in study area mainly are compaction, cementation, secondary outgrowth cementation and filling of authigenic mineral. The compaction of sandstone was mainly middle to deep. The constructive diagenesis mainly comprised metasomatism, alteration, dissolution and rupture.3. The pore types of the sandstone of reservoir in study area comprised primary intergranular pores, intergranular corrosion pores, dissolution pores, micro-pores and cracks. By the observation of pore types of thin sections, characteristics, capillary pressure curve, parameters of pore structure, the reservoir of Shan 1, He 8 in the north Sulige can be divided into reservoir of combination of medium to micro pore throat, reservoir of combination of medium, small-tiny pore throat, reservoir of combination of porous and micro pore throat. The main type of pore throat is medium or small-tiny.4. The statistical analysis to properties of 9511 sandstone samples from 89 wells in north Sulige, which include well Su 44 and well Tong 5, indicate that sandstone reservoir of study area mainly are especially low porosity and low permeability ones, secondarily are low porosity and low permeability ones, and few low porosity and low permeability, ones of especially low porosity and low permeability and middle porosity-middle permeability. Porosity and permeability relevance analysis from core sample determination and well logging interpretation indicated that permeability is positive correlation with the porosity in north Sulige, which manifested that permeability change was controlled by porosity, the porosity was better, the permeability was better, that is the characteristic of pore reservoir. In braided river, the properties of channel bar is best, the properties of flood plain is relatively worse; In meandering river, the properties of riverbed lag sediment and point bar is best, the properties of natural levee is secondly best, the properties of washland and flood lake is worst.5. The distribution of sandbody in study area was asymmetry, the layer of sandbody in different well was not the same, and the thickness was distinct, therefore the reservoir heterogeneity of thin interval of Shan 1 to upper He 8 member was very obvious in research area. The rhythmicities of permeability mainly are positive rhythm, inverted rhythm, isotropic, composite and stochastic, the composite rhythm is the predominant type, and the positive rhythm is most common. The areal heterogeneity of sandbody permeability is very serious. Upper He 8 member was most serious, the second was lower He 8 member and then was Shan 1 member. Evaluated by the index of variation coefficient, mutation coefficient and permeability difference,no matter by the result of rock core determination data or by logging interpretation, they both indicated that the heterogeneity of sandstone reservoir of Shan 1 member and He 8 member is relatively obvious.6. Based on of pore type, diagenesis, reservoir characteristic and classification evaluation, comprehensive analysis of sedimentary microfacies, effective thickness, porosity, permeability, it can be divided into four kinds of favorable reservoir, the typeâ… was the favorable reservoir, the typeâ…¡was relatively favorable reservoir, the typeâ…¢was normal reservoir, the typeâ…£was bad reservoir. According to this standard, the favorable areas of He 8 member in the north Sulige gas filed were filtered, the favorable area mainly distributed in the channel sandbody, the favorable typeâ… and relatively favorable area typeâ…¡could be the key area for the next exploration.