Analysis On The Correlation Of Different Types Of Oil And Gas Reservoirs In Mesozoic And Paleozoic In Ordos Basin

Ordos Basin is the basin with the highest oil and gas production in China at present.The oil reservoirs are mainly distributed in the Chang 10-chang 1 member of the Mesozoic Yanchang Formation and the Yan'an formation,and the oil source is mainly the Chang 7source rock.The gas reservoirs are mainly distributed in the Paleozoic Shiqianfeng Formation,Shihezi Formation,Shanxi formation,Taiyuan formation,Benxi Formation and Majiagou formation.The gas source is mainly the coal measure source rocks of Shanxi formation,Taiyuan Formation and Benxi Formation.At present,the types and distribution of the discovered reservoirs or gas reservoirs are different in different strata,and the corresponding exploration degree is very uneven.At present,the correlation research on the distribution of different types of oil and gas reservoirs in different strata is weak,which restricts the further comprehensive exploration of the area.Based on a large number of geological,seismic,logging and logging data,this paper analyzes the relationship between the discovered oil reservoirs of Yanchang Formation and Yan'an formation and Chang 7 bottom sag uplift combination structure,Chang 7 bottom sag uplift combination structure and sand body combination,and Chang 7 bottom sag uplift combination structure and fault combination.The relationship between Paleozoic gas reservoir and Taiyuan Formation bottom sag uplift combination structure,Taiyuan Formation bottom sag uplift combination structure and sand body combination,Taiyuan Formation bottom sag uplift combination structure and fault combination are also analyzed.On this basis,the correlation between different types of reservoirs in different strata of Mesozoic and different types of gas reservoirs in different strata of Paleozoic is analyzed.(1)Distribution correlation of different types of reservoirs in Yanchang and Yan'an formations of Mesozoic.According to the relationship between sandbody strike and sag uplift combination structure of Chang 7 source rock,the sandbodies of Chang 6 and Chang 7 members can be divided into four types,lenticular sandbodies(The sand body is lenticular and surrounded by mudstone),shunpo sandbodies(The end of the extension of sand body points to the low part of the structure,and the trend of sand body intersects with the contour of structure),nipo sandbodies(The pinchout end of the sandbody extension points to the high part of the structure,and the strike of the sandbody is obliquely intersected with the structural isoline),hengpo sandbodies(The strike of the boundary on the updip side of the sand body is nearly parallel to the structural contour).At present,the discovered sandstone reservoirs of Chang 6and Chang 7 members are mainly distributed in hengpo sandbodies in the present tectonic evolution stage,and the relationship between these sandbodies and structures will change in the late Early Cretaceous and late Cretaceous Neogene tectonic evolution stages.According to the corresponding relationship between gas logging total hydrocarbon curve and sandstone and mudstone of Chang 6 and Chang 7 members,they can be divided into two types.The first type has high gas logging total hydrocarbon value in sandstone member,and the second type has high gas logging total hydrocarbon value in both sandstone and mudstone member.Among 215 intervals of 112 wells with gas logging display in Chang 7member,134 intervals of 92 wells have the second type of characteristics,and the interval of Chang 6 member with the second type of characteristics is slightly less than that of Chang 7member,which indicates that oil-bearing of sand shale superimposed combination is an important feature of Chang 6 and Chang 7 reservoirs.The discovered reservoirs of Chang 4+5,Chang 3,Chang 2,Chang 1 and Yan'an formation and Chang'an group 8,Chang 9 and Chang 10 are mostly distributed on or near faults.Most of these faults are cut with Chang 6 and Chang 7 sandstone reservoirs.In addition,22 chang7 shale oil wells with industrial production capacity are distributed on or near faults.(2)Distribution correlation of different types of gas reservoirs in Shiqianfeng,Shanxi,Taiyuan and Majiagou formations of Paleozoic.According to the relationship between the strike of sandbodies and the basement uplift combination structure of Taiyuan formation,the sandbodies of Shihezi Formation,Shanxi formation,Taiyuan Formation and Benxi Formation can be divided into four types:lenticular sandbodies,shunpo sandbodies,nipo sandbodies and hengpo sandbodies.At present,the discovered sandstone gas reservoirs of Benxi Formation and some Taiyuan formation are mainly distributed in lenticular sandbodies.The discovered sandstone gas reservoirs of Shihezi Formation,Shanxi Formation and some Taiyuan formation are mainly distributed in hengpo sandbodies in the present tectonic evolution stage.The relationship between these sandbodies and structures will change in the late Cretaceous Neogene tectonic evolution stage.According to the corresponding relationship between gas logging total hydrocarbon curve and sandstone and mudstone(including coal seam)of Shihezi Formation,Shanxi formation,Taiyuan Formation and Benxi Formation,they can be divided into two types.The first type has high gas logging total hydrocarbon value in sandstone section,and the second type has high gas logging total hydrocarbon value in sandstone and mudstone section.Among the 2165 intervals of 524 wells in Shihezi Benxi Formation with gas logging,1430 intervals of 450 wells have the second type characteristics,which indicates that the gas bearing of sand shale superimposed combination is an important feature of Shihezi Benxi Formation.This paper analyzes the relationship between more than 1000 high-yield gas wells(with daily gas production of more than 50000 m~3)discovered in the upper Paleozoic and lower Paleozoic in the basin and faults.More than 90%of the high-yield wells are distributed on or near faults.The gas reservoirs of Shiqianfeng Formation are cut by faults,and these faults also cut the sandstone gas reservoirs of Shihezi Formation Benxi Formation.According to the characteristics of gas logging total hydrocarbon curve of Taiyuan formation,Benxi Formation and Majiagou formation,the types of total hydrocarbon curve are divided into continuous type(continuous high value of gas logging total hydrocarbon from Benxi Formation to Majiagou formation)and separate type(high value of gas logging total hydrocarbon in Benxi Formation and Majiagou Formation,but discontinuous value of gas logging total hydrocarbon).Of 269 wells with gas logging curve in Majiagou formation,212wells have continuous characteristics,which indicates that these Majiagou gas reservoirs have overlapping correlation with Taiyuan group and Benxi Formation gas reservoir.57 wells have the characteristics of separate type,and these wells are distributed on or near the fault in the plane,indicating that these Majiagou Formation gas reservoirs have fault correlation with Taiyuan Formation and Benxi Formation gas reservoirs.