Quantitative Researches Of Diagenesis Of Deep Buried Clastic Reservoirs In The Shiwu Depression

The deep buried reservoir is the most important exploration area in the Shiwu depression, where the final aim of deep buried reservoir finds secondary pore growth zones. The distribution of secondary pore with deep in the different sedimentary basin has become the main quention and content of oil and gas exploration today. The researches of secondary pore growth zones provide more chances for looking for oil and gas reserves of deep buried reservoir and promote the researches of diagenesis. Thus, the study in evaluation of reservoir field is being more and more attracted people's attention. We attempt to analysis diagenetic field and predict diagenetic facies by studies on diagenetic modeling. Then the secondary porosity genesis and its influencing factors are discussed and high porosity zones are predicted by the comprehensive studies on diagenesis, diagenetic facies and sedimentary facies of deep buried reservoir in the Shiwu depression.Diagenetic modeling is the most important part of the quantitative evaluation of reservoir. At first, we separately introduce uniterm diagenesis process oriented-vitrinite reflectance, the changing rules of sterane isomerization rate, clay mineral transformation, quartz overgrowth and mechanical compaction. Then aggregative diagenetic process oriented are discussed on the basis of the uniterm diagenesis process oriented. So all the diagenetic stage of clastic rock are numerical from zero to one, and voluntarily divided by computer in time and space.As the results of the diagenesis modeling researches show, the deep buried reservoirs in the Shiwu depression can be divided into the early diagenetic stages, the middle diagenetic stages and the late diagenetic stages, aggregately five subphases. that is to say: the early diagenetic phase A, the early diagenetic phase B, the middle diagenetic phase A1,A2 and the middle diagenetic phase B. It can be divided dominantly into four diagenetic facies, the early compaction and cementation, dissolution, dissolution and partial recementation, strong compaction and fractures diagenetic facies. Three high porosity zones are developed in the vertical orientation, which distributed in the formations from 400m to 800m,from 1400m to 2000m and from 2200m to 2800m.They almost occurre in the sandstones of delta plains, fan-delta plains, floodplains and fan-delta plains. According to the analysis of the factors of the high porosity zones formation, we believe that the first high porosity zone formed by dissolution of meteoric waters, the second and the third one formed by dissolution of organic acids and dehydration of clay minerals. Porosity isn't obviously affected by early hydrocarbon invasion and clay rims. The areas developed favorable and the relatively favorable reservoirs of the high porosity zones are blocked out in the horizontal orientation by the comprehensive studies on constrained sparse spike inversion acoustic impedance map, sand strata ratio, diagenetic facies and sedimentary facies.