Reservoir Characteristics And Controlling Factors Of The Igneous Rock In Chengdao-Zhuanghai Area

Chengdao-Zhuanghai area is located in the intersection area of Jiyang Depression and Bozhong Depression,which is above a large buried mountain mantle tectonic belt.Since the 1980 s,industrial oil flow was been obtained at Chengdao-Zhuanghai area in Mesozoic igneous strata by Shengli Oilfield.With the development of exploration,Mesozoic buried mountain plays an increasingly important role in the exploration strata of Shengli Oilfield.Igneous reservoir is also widely concerned and it becomes a new frontier of oil and gas exploration.However,there are some problems in this area,such as lack of relevant studies on igneous rocks,different classification standards of igneous rocks,different types of reservoir space,characteristics and main controlling factors.Moreover,these factors restrict the exploration work nowadays.Thus,the study of Mesozoic igneous rocks in the area is helpful to further study on Mesozoic reservoir and it also provides geological basis for the exploration of igneous reservoir.On the basis of comprehensive analysis of previous studies,reservoir characteristics and controlling factors of the igneous rock in studied area are studied through detailed description of core and systematic collection of samples.Based on petrology,element geochemistry,well logging,seismic and other geophysical data,the lithology and lithofacies,Reservoir space types and controlling factors of oil and gas accumulation in the Mesozoic igneous rocks are researched.The types of igneous rocks and lithofacies in studied area are defined.the reservoir space types in studied area are divided,and the controlling factors of igneous reservoir development are discussed.The following results are obtained:(1)There are no intrusive rocks in studied area.Volcanic rocks are divided into 6 categories and 13 subcategories.According to the proportion of thickness,the major types of lithology are volcanic lava > pyroclastic rock >sedimentary pyroclastic rock > pyroclastic lava > vein rock > subvolcanic rock;Petro facies can be divided into 4 types and 6 subfaces.According to the proportion of thickness,the major types of lithofaces are overflow faces>subvolcanic facies> eruptive facies>volcanic sedimentary facies;(2)The cross plot of GR-M can be used to identify igneous rocks from sedimentary surrounding rocks.Logging values such as GR,SP and AC can help identify specific lithology,and the coincidence rate is up to 96.81%;This paper extracts seismic attributes in Zhuanghai2017 seismic area,and predicts lithological plane distribution in Zhuanghai area.Compared with drilling lithology,the coincidence rate can reach 91.3%.(3)The macroscopical reservoir space of igneous rock is dominated by fractures,while the microcosmic reservoir space is dominated by matrix dissolved pores and porphyry dissolved pores;The reservoir space is mainly fissure-pore type and fracture type reservoirs;A set of evaluation criteria and methods for volcanic rock reservoirs in studied area were formed,and the plane distribution of reservoirs was predicted.(4)The controlling factors of reservoir development in studied area are mainly lithologic lithofacies and tectonic movement,and the influence of cycle period is weak.The lithology and lithofacies of igneous rocks affect the types of pores,fractures and the development of late stage,and are directly related to the oil-bearing reservoir.The control of igneous rock in Chengdao-Zhuanghai area by tectonic activity in Himalaya period is the most important.The structural fractures and micro-fractures generated by the multistage fault activities in the fissure-lithologic oil and gas reservoir communicate with the primary pores of the volcanic rock and form effective reservoirs.The main reservoir rocks are the overflow facies andesite.Unconformity-lithologic oil and gas reservoirs are influenced by ancient topography and landform,and the weathering and leaching under unconformity are strong.