Study on a New Method of Fluid Damage Assessment for Complex Lithologic Reservoir

In this paper, a new method of fluid damage evaluation is established to solve the problem of low success rates of sensitivity evaluation experiments of the complex lithologic reservoir such as irregular samples, tight samples, weak cementation, and strong expansibility. Based on the irregular samples, the micro visual evaluation technology of scanning electron microscope for fluid damage in the well is established. A new method of Pal’s experiment + expansion experiment is established to solve the problem of the processing of the plunger sample with weak cementation or strong expansion. To solve the problem of a low success rate of tight core flow experiment, the sensitivity evaluation method of “main pressure failure” was established and the attention index was selected as the sensitivity evaluation index. The micro-damage mechanism of the fluid entering the well for the reservoir is clarified. The expansion efficiency is converted into permeability loss to realize the static quantitative evaluation of the damage degree of the fluid entering the well. The sensitivity of attention index evaluation expands the technical lower limit of permeability evaluation and greatly improves the success rate of tight core fluidity experiments. The combination of the three evaluation techniques can effectively solve the problem of damage evaluation of complex lithologic reservoirs, which can be widely used in major oil fields and provide data support for drilling fluid optimization and injection production system optimization.