大港油田气藏盖储压力差对天然气富集的控制作用

CONTROLS OF THE CAPROCK-RESERVOIR PRESSURE DIFFERENCE ON THE NATURAL GAS ACCUMULATION FOR THE GAS RESERVOIRS IN DAGANG OILFIELD

为了研究大港油田天然气的形成条件，在盖层排替压力差与剩余压力研究的基础上，通过气藏盖储压力差与储量丰度之间关系分析，研究了21个气藏的盖储压力差对天然气富集的控制作用。结果表明：大港油田气藏的盖储压力差为-43．26～25．73MPa，气藏盖储压力差小于0MPa，不利于天然气在气藏中聚集与保存；盖储压力差对气藏天然气富集具有明显的控制作用，盖储压力差越大，气藏储量丰度越高；在气源充足条件下，大港油田形成高、中、低储量丰度气藏所需的最小盖储压力差分别为8．4、-4．1、-21．0MPa。

In order to study the accumulating conditions of the natural gas in Dagang Oilfield, on the bases of the researches between the displacement pressures of the caprock and residual pressures of the reservoir, the control of the caprock-reservoir pressure differences on the gas accumulation for 21 gas reservoirs are studied by analyzing the relationship between the pressure difference and gas reserve abundance. The achievements show that the pressure difference range is from-43.26 MPa to 25.73 MPa, when the differences are less than zero MPa, the gas is disad- vantageous to accumulate and preserve in the gas reservoirs; the pressure differences possess obvious control on the gas enrichment, the greater the differences are, the higher the abundance will be ; under the conditions of sufficient gas supply, the needed minimum pressure differences between the caprock and reservoir are respectively 8.4 MPa, -4. 1 MPa and-21.0 MPa for the high, middle and low-reserve-abundance gas reservoirs in Dagang Oilfield.