一种超高压致密油气藏地层压力条件渗透率的实验室测量新方法

New measurement method of permeability under the pore pressure condition of rock sample of ultrahigh pressure tight reservoir

实验观测超高压致密油气藏的地层压力条件的渗透率对于定量表征储层物性以及制定开发方案具有重要意义.常规的方法采用在岩心的出口端设置回压阀的方式实现孔隙压力的控制和流量的计量,存在回压阀控制孔隙压力精度低、灵敏度低、流量计量不准确的技术缺陷,渗透率测量精度低.在岩心的出口端使用高精度恒速恒压泵代替回压阀,开发了一种基于高精度恒速恒压泵双泵联动控制孔隙压力及流量/压力计量技术的渗透率测量新方法,通过岩心的入口端和出口端的两台高精度恒速恒压泵做进液、退液的联动操作计量恒压模式的进液/退液体积或者恒流量模式的上游压力/下游压力实现超高压渗透率的测量.在最高为138 MPa的超高压条件下,实验观测了准噶尔盆地白垩系清水河组的超高压致密油气藏的5块岩样的地层压力条件的渗透率,结果发现:低地层压力条件下的渗透率测量结果与相同有效压力的覆压渗透率吻合较好,超高压条件下的渗透率重复性好并且符合渗透率随有效压力变小而变大的一般规律.

It is very important to measure the permeability under the formation pressure condition of rock sample of ultrahigh pressure tight reservoir for the reservoir characterization and prediction.The normal method with back-pressure valve technology for exerting pore pressure and measurement of flow was not able to gain ideal permeability precision because of low control precision of pore pressure,low sensitivity,and low measurement precision of flow.A new measurement method of permeability was developed through the flow linkage of 2 high precision constant pressure and speed pumps located both sides of rock sample for exerting pore pressure and measurement of flow or pressure,in which the back-pressure valve at the end of rock sample was replaced by a high precision constant pressure and speed pump and the permeability can be calculated by the measurement of flow in the mode of constant pressure or the measurement of differential pressure in the mode of constant flow.Under the ultrahigh pore pressure condition up to 138 MPa,the permeabilities of 5 rock samples from ultrahigh pressure tight reservoir of Qingshuihe Formation of Lower Cretaceous in southern margin of Junggar Basin were measured with the employment of new method.The results showed that the permeabilities measured by new method match the permeabilities measured by overburden pressure method good under the low pore pressure condition and good reproducibility of the measurement and positive correlation between permeability and effective pressure under the ultrahigh pressure condition.