Characteristics Of Karstification Reservoir And Gas-water Distribution Relationship Of Majiagou Formation In T2 Area,Sulige Gas Field

The ordovician majiagou formation of the lower Paleozoic gas reservoir in T2 block the main target strata.Lack of reservoir characteristics and classification criteria of target strata;Gas and water distribution law is not clear and so on.In view of the above problems,this paper analyzes and studies the reservoir characteristics and gas-water distribution law of the ordovician majiagou formation from the perspectives of stratigraphic division and correlation,present structural characteristics of main structural interfaces,recovery of weathered crust and karst paleogeomorphology,and reservoir characteristics and distribution.This paper mainly studies the relationship between the characteristics of upper assemblage karst reservoir and gas and water distribution in tao2 block,which provides scientific basis for the development of ordovician majiagou formation in tao2 block,sulige gas field.The main achievements are as follows:?1?The strata of the lower ancient majiagou formation in T2 block are relatively well preserved.Except for the sixth section of the ma formation,the exposed strata are mainly ma5 ₁₊₂.The thickness of each small layer in the study area is relatively stable and the region is relatively strong.On the whole,the strata in the west and north of the study area are greatly affected by tectonic uplift and denudation.The denudation effect in the middle and south is weak and the strata are relatively intact.?2?There are obvious inheritability between the current structures of marker layers K1and K3 in T2 block,which is manifested by the development of a series of NE and NEE compound nasal structures on the gentle western monoclinal background,and they are arranged in an en echelon pattern.The ordovician karst paleogeomorphology is characterized by the distribution pattern of"high in the west and low in the east,high in the north and low in the south".The pre-carboniferous palaeogeomorphology in the study area can be characterized into 2 types of secondary units and 11 types of tertiary units by using the comprehensive method.?3?The reservoir as a whole is characterized by low porosity,low permeability and strong heterogeneity.Majiagou group on the combination of reservoir in the study area for the synthetic evaluation of classification,the quality difference is big,small layers of oil reservoir is given priority to with?+?type reservoir,?class reservoir more scattered distribution in ma5and ma5₄¹.?4?The karst uplands in T2 block are mainly distributed in the west and northwest of the study area.The corresponding palaeotopography and palaeotopography are relatively high on the whole,and are mainly composed of plateaus,residual hills,terraces and depressions.From the perspective of reservoir distribution characteristics,the ma5₁₊₂ and ma5₁³reservoirs are generally absent in the northwestern karst upland development zone,and only ma5₄¹dolomite reservoirs are developed.Karst slope is a favorable location for effective reservoir development in T2 block,occupying most of the central,eastern and southern parts of the study area,with a wide distribution range.The dolomite reservoirs of influence of burial depth and fresh water leaching,the reservoir physical properties of the main production area in the study area.?5?There are four distribution patterns of combined gas and water distribution in the majiagou formation in T2 block:pore residual water,lithologic gas reservoir retained lens water,structural lithologic gas reservoir relatively water-rich gas reservoir residue,and structural gas reservoir water-rich gas reservoir residue.Among them,the tectonic gas reservoirs are mainly distributed in the nose of the forward structural belt,the lithologic gas reservoirs are mainly distributed in the local areas with good reservoir physical properties in the ma5 ₁₊₂ submember,and the tectonic-lithologic gas reservoirs are mainly distributed in the ma5₄¹ small formation in the western part of the study area.?6?The distribution of gas and water in T2 block is uneven in the vertical and horizontal directions.The high part of the structure is dominated by gas-producing Wells,while the low part is mainly dominated by gas-water co-producing Wells.The gas layer is distributed in the sub-sections of ma5₁,ma5₂ and ma5₄.On the plane,the gas-producing Wells are mainly distributed in the northwest and south-central regions of the study area,and the gas-water co-producing Wells are mainly located in the middle part of the study area.In general,high-yielding Wells are mainly developed in the north,east and southeast of the study area.Gas-water co-production Wells are mostly distributed in secondary residual hills and upper slopes.The Wells are mainly distributed in low-lying areas such as terraces,depressions and lower slopes.