鄂尔多斯盆地储集层物性断裂对超低渗油气藏的控制作用

Controlling of petrophysical fractures on extra-low permeability oil and gas reservoirs in Ordos Basin

在鄂尔多斯盆地的野外地质调查和钻井岩心观察中,发现砂岩中发育大量的雁行状和X共轭状节理、裂缝、微裂缝以及局部断裂,以“超稳定地块”为前提的传统构造学说无法对此做出合理的解释。研究发现,基底断裂及后期构造活动衍生的一系列剪切变形所产生的储集层物性断裂对油气的控制不容忽视。鄂尔多斯盆地中,所谓“超低渗透”是指基质渗透率,不能代表地层总渗透率。储集层中剪切、挤压等构造应力产生的节理以及沿这些微破裂派生的溶蚀孔缝形成良好物性区带才是油气相对高产的主要原因。因此,在寻找勘探靶区时应重视构造因素对成岩作用、酸性流体输导、次生溶孔形成等的控制作用。

In geological survey and core observation in Ordos Basin, structures as echelon joints, X conjugated joint.s, fractures, micro-fractures and local ruptures were found well developed in the reservoir sandstones. It cannot be explained by the traditional tectonics theory based on Ultra-steady Block. The tectonic movement direction, the petrophysical property of sandstone, and the oil and gas distribution were subjected to the succe.ssive activities of deep and big faults in the basin basement. The regional tectonic stress field also influences them. The low permeability reservoir reflected by the matrix does not represent the real permeability of the reservoirs. The oil and gas distribution is .subjected to the reservoir petrophysical fractures, reflected by the features of a series of shear deformation derived from the base ruptures and late tectonic activities. The emphasis should be put on understanding how tectonic factors control the diagenesis, the acidic liquid transporting, and the formation of secondary solution pores in the future exploration.