Research On Reservoir Characteristics Of The He-8 Member At Zhao 30 Wellblock In Sulige Gas Field Of Ordos Basin

This paper takes the theory of sedimentology and reservoir geology as a guidance, through the core observation and a lot of rocks thin section identification, combined with the data of test analysis such as cathodoluminescence, SEM, X-ray diffraction of clay mineral analysis, physical properties and mercury injection etc. to study the sandstone reservoir of He-8 member at Zhao 30 wellblock in Sulige gas field of Ordos Basin systematicly. Mainly studied the reservoir petrology features, diagenesis, reservoir physical properties characteristics and the reservoir controlling factors, and screened the favorable areas in the study area.Through the comprehensive research of the sandstone reservoir we can get the cognitions as below:The provenance of study area is the Alxa-Yinshan ancient land of the northern margin to the northwestern margin of Ordos Basin. He-8 lower segment mainly develop braided river sedimentation, He-8 upper sub-member gradually change from braided river sedimentation to meandering river deposition.The results of reservoir petrology study in Zhao 30 wellblock He-8 member show that:lithic quartz sandstone and lithic sandstone are the mainly reservoir rock types, quartz sandstone is subordination.The type of detrital minerals has low feldspar and rich lithic content, with slightly high compositional maturity. The clay matrix, calcite, siliceous and clay cement are the mainly interstitial material types, the cement is the based interstitial structure and is pore cementation type.The results of diagenesis study in Zhao 30 wellblock He-8 member show that: compaction/pressure solution effect and cementation play a destructive role in development of reservoir porosity, metasomatic alteration palys a keeping role, dissolution and fracture diagenesis play a constructive role. The subject of diagenetic stage has already been in stage B of the middle diagenetic stage to early of late diagenesis stage.The results of reservoir physical properties characteristics study in Zhao 30 wellblock He-8 member show that:there are many pore types such as intergranular pore, intergranular dissolved pore, feldspar dissolved pore, lithic dissolved pore, intercrystalline pores and microcracks. The reservoir pore texture is poor, and the mixed pore with remnants primary pore and secondary pore are the mainly pore-types of study area reservoir. The porosity and permeability has a positive correlation in the sandstone reservoir of He-8 member,and the distribution of the high porosity value wells and the high permeability value wells have a good agreement, which explains that the development degree of reservoir porosity controls the size of the reservoir flow capacity, He-8 member is porous reservoirs.He-8 member sandstone reservoir of the study area was controlled by the source and properties of the rock, sedimentary environment and diagenesis. Reservoir properties in different types of sandstone have obvious differences and obviously phased law. The results of calculation show that the porosity loss rate of He-8 reservoir range from 17.4% to 22.6% due to the compaction, other diagenesis on reservoir properties also showed varying degrees of impact.Comprehensive the results of all studies and consideration of all aspects of reservoir parameters in the study area, the reservoir divided into four categories, they are favorable reservoir(?class), less favorable reservoir(?class), medium reservoir(?class) and poor reservoir(?class). By screening the favorable exploration zone of He-8 member in the study area show that favorable exploration area is mainly distributed in the channel sand body, such as the channel bar of braided river and the point bar of meandering river, the ?class and ?class reservoirs are the key exploration area.