Fine Description Of Triassic Baikouquan Formation Reservoir In Ma 18 Well Block Of Mahu Oilfield

Since the oil reservoir of BaiKouQuan Formation in Ma 18 well area was put into production,many problems have gradually emerged:the sedimentary facies has low precision and insufficient understanding;reservoir development has poor regularity and large lateral variation;the quality reservoir evaluation parameters are single,and the main controlling factors for the existence of high-quality reservoirs are not clear.,etc.It is necessary to systematically carry out research on fine reservoir description.Based on the above problems,this paper makes use of the theory of structural geology,sedimentary petrology,and development geology as a guide to comprehensively apply drilling data,logging data,seismic data,analytical tests,and utilize various technical means to characterize the stratigraphic characteristics,structural characteristics,sedimentary facies characteristics,reservoir characteristics and oil pool characteristics of Baikouquan Formation in Ma 18 well area.Finally,the three-dimensional geological model of the reservoir was established,and the reservoir scale and reserves abundance are defined and the favorable target area was optimized.And the following achievements and understandings are obtained:1)The Baikouquan Formation in Ma 18 well area is divided into three sections from bottom to top.The fist section and second section of Baikouquan formation are further divided into three groups of glutenite layers.The logging curves are serrated,representing the overlapping of high-resistivity glutenite and low-resistivity mudstone.In seismic data,the wave impedance of the reservoir of the second section of Bai Kou Quan formation shows medium-strong amplitude peak reflection and good continuity;the wave impedance of the reservoir of the first section of Bai Kou Quan formation shows medium-weak amplitude peak reflection and medium continuity.The regional stratigraphic distribution is stable and the thickness varies slightly.2)The Baikouquan Formation in Ma 18 well area is a monoclinic structure that is inclined to the southeast.The dip angle of the formation is 1°-2.5°,and it is cut by two sets of closed reverse faults with a distance of 10-40m.The top of Baikouquan Formation in Aihu 1 Fault Block is NW-SE monoclinic structure,while the top of Baikouquan Formation in Ma 18 Fault Block is a nose-like structure of middle-high and low on both sides.3)The Baikouquan Formation in Well Ma 18 Well area is mainly located in the front of Huangyangquan fan delta,often underwater,and only exposes to the surface in dry season.The fist section and second section of Baikouquan formation are mainly recognized as underwater distributary channel and interdistributary bay deposit.while the third section of Baikouquan Formation are recognized as the front fan delta.The lithology of underwater distributary channel is mainly thick gray-green sandy medium-fine conglomerate.Logging curves are usually bell-shaped or box-shaped.4)The reservoir lithology of the fist section of Baikouquan formation is mainly fine conglomerate and small conglomerate,while the second section of Baikouquan formation is medium conglomerate and fine conglomerate.Reservoir space is dominated by intragranular corrosion pore,the capillary radius is fine,and the microporous micro-fine throat is the main one.The displacement pressure is medium-high and the pore structure is medium-poor.The average porosity of the reservoir is about 10%,and the average permeability is about 2.7mD.It is a low-porosity and ultra-low-permeability reservoir as a whole.Controlled by the sedimentary microfacies,the glutenite of reservoir are distributed in an irregular band along the direction of the source.The study of four-property relationship shows that oil-bearing properties are mainly affected by reservoir lithology and physical properties.The Aihu 1 fault block and the Ma 18 fault block Baikouquan Formation are fault-controlled lithologic-structural reservoirs.5)Based on the combination of well drilling and seismic data,the high-precision structure models,sedimentary facies models and attribute models were established.The volumetric method provided by Petrel software was used to calculate the reserves.The proven oil geological reserves of the Aihu 1 fault block and the Ma 18 fault block reservoir are 3291.68×104t.The average abundance of the Ma 18 fault block is greater than 65.63×104m3/km2,and the average abundance of the Aihu 1 block is 93.75×104m3/km2,which is a low reserve abundance.