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由于储层具有较强的压力敏感性,很多深层复杂低渗透油藏的生产过程中,存在产量递减速度快、注不进采不出等问题。许多油田通过储层压力敏感性评价实验,评价结果为弱压力敏感或无压力敏感,但在实际开发过程中体现出强压力敏感性特征,实验室压力敏感性评价结果偏离实际油藏真实情况。导致实验室所测压力敏感性比处于高压下的储层压力敏感性弱的主要原因:一是异常高压油藏储层渗透率压力敏感的时滞效应,另一点是开采过程中孔隙度和渗透率损失的不可逆性。为了准确评价储层应力的敏感性,实验室需使每个围压点保持相应的时间以保证测试的渗透率已稳定;实验所用岩心必须是在储层原始状况下取出的岩心;针对异常高压低渗透油藏,如果使用的是地层压力下降后的储层岩心,建议在使用相同裂缝密度且渗透率大20%~40%的岩心进行实验。
Due to the strong pressure sensitivity of reservoirs, many deep complex low-permeability reservoirs have problems of rapid decline of production rate and failure of recovery of production during the production process. Many oilfields have passed the reservoir pressure sensitivity evaluation test, and the evaluation results are weak pressure-sensitive or pressure-less sensitive. However, they are characterized by strong pressure sensitivity in the actual development process. Laboratory pressure sensitivity evaluation results deviate from actual reservoir conditions. The main reasons leading to the sensitivity of the laboratory to the measured pressure sensitivity are lower than that of the reservoir under high pressure. The first is the pressure-sensitive time-lag effect of the permeability of the abnormally high pressure reservoir and the other is the porosity and infiltration Irreversibility of rate loss. In order to accurately evaluate the sensitivity of reservoir stress, the laboratory needs to make each confining pressure point maintain the corresponding time to ensure that the permeability of the test has been stabilized. The core used in the experiment must be the core removed under the original condition of the reservoir. For low-permeability reservoirs, it is recommended to use cores of the same fracture density and permeability of 20% to 40% if using reservoir cores with decreased formation pressure.