Evaluation Of Geological Sweet Point Of Conglomerate Reservoir In Baikouquan Formation,Fengnan 4 Block Around Mahu Sag

In order to alleviate the contradiction between China’s oil and gas supply and demand,in addition to the development of new energy,it is necessary to accelerate the exploration and development of oil and gas in unconventional fields.Tight oil and gas are the most realistic resource in the field of unconventional fields in China.Dividing the "sweet point" can provide strategic guidance for the exploration and development of tight oil.The newly discovered 1 billion tons of tight conglomerate oil and gas reserves in the Mahu area of Xinjiang has enhanced the position of tight conglomerate in the tight sandstone family.However,the rock has large grain size,poor sorting and heterogeneity,so the reservoir capacity difference is large and the favorable zone is unclear.Therefore,it is especially important to predict the“sweet point" of the reservoir.The basis for evaluating reservoir“sweet point" is to identify reservoir geological“sweet point" by establishing a set of“sweet point" predicted research methodsThis paper takes the Fengnan 4 block of Mahu Sag in Junggar Basin as an example to carry out physical property test,microscopic qualitative observation（casting sheet,scanning electron microscope）,and reservoir quantitative characterization experiment（nitrogen adsorption,constant velocity mercury intrusion,high pressure mercury intrusion）.,nuclear magnetic resonance,whole rock and clay minerals)and fluid mobility tests（nuclear magnetic-centrifugation experiments and nuclear magnetic-displacement experiments）,based on physical properties,oil-bearing properties,mobility and pore-throat structure evaluation,establish porosity,The oil saturation log evaluation model uses the oil porosity as the evaluation parameter to carry out the identification and evaluation of the geological“sweet point" and to clarify the quality and distribution of the geological sweet point in the study areaThe results show that residual intergranular pore,secondary dissolution pore,intergranular pore and grain margin fracture are mainly developed in the compact conglomerate in the study area.The geological "sweet point" classification scheme of Mahu tight conglomerate reservoir is divided into four categories,i.e.type I“sweet point","type Ⅱ“sweet point","low-efficiency reservoir"and non-reservoir.The sampling points in this area are type Ⅱ "sweet point","low-efficiency reservoir" and non-reservoir.（1）type Ⅱ“sweet point"（?）>15%,K>2×10-3μm2,mainly developed micron residual intergranular pore and secondary dissolution pore;pore throat structure is pore throat co-controlled type,throat radius distribution is 1-3 μm;NMR curve is high left single peak type,movable oil exists in micropore to macropore;particle size is small.（2）"low-efficiency reservoir"（?）ranges from 5.5%to 15%,K from（0.25～2.8）×10-3μm2,mainly develops micro-nano-scale intragranular dissolved pore;pore throat structure is throat-conducting type,throat radius is less than 1.8μm;NMR curve is medium-single peak type,movable oil occurs in micro-pore to larger pore;particle size is larger.（3）Non-reservoir（?）is between 4.6%～7%,K is between（0.04～1.3）×10-3μm2,only locally developed nano-scale intragranular dissolved pore;throat-controlled,throat radius is less than 1.6 μm;NMR curve is low-left single peak,movable oil content is small,mainly in small and micro-pore;particle size is large.The Baikouquan Formation in Fengnan 4 well area is dominated by type Ⅱ desserts with a small amount of type Ⅰ desserts,mainly distributed in T1b21 and T1b3.（1）Type Ⅱ desserts are widely developed in T1b2,and gradually thinning around the well Fengnan 15.Type Ⅰ desserts are distributed in a circular strip in the west.（2）Type Ⅱ are developed gradually from north to south in Tib3,while type Ⅰ desserts only developed locally and were thin layer.（3）Only thick type Ⅱ dessert and thin layer type Ⅰ dessert are developed in well Fengnan 4 in T₁b₁.