New methodology for analysis of performance for diverting agents in unconsolidated sandstones in real time with physical simulator using computed tomography

摘要

While oil and gas wells have the advantage of being able to expel naturally damaging particles produced during the drilling and/or completion phase, water injector wells are prone to accumulating particles up to their completion. In order to remove these particles and restore the potential injectivity of these wells, acid treatments are usually required. One of the major challenges of these operations is to accomplish treatment diversion. If the interval consists of layers with different permeabilities, the acid will preferably penetrate high-permeability layers, leaving the zones of minor permeability without treatment. Even if the reservoir is not a homogeneous one, the damage may not be uniformly distributed and the lack of a good method to obtain a better acid distribution may not be able to remove a significant part of the damage, since acid will penetrate only areas with minor damage. To enable diversion, a highly effective material quantity and concentration is required. The diverting agent must also be non-damaging, low-cost and easy-to-use. The diverting agent studied has shown a good performance for permeabilities up to 3 Darcy. The main advantage of the diverting agent, besides its high-divergence capacity, is the specific action that forms channels into the pores of the reservoir where only oil can flow due to the high-hygroscopic characteristic that capture the water around the pores. And finally the diverting agent after treatment has the capability to remove itself along with the oil produced in treated wells. This eliminates the need for subsequent treatments that would increase time and cost. In this study, X-ray Computed Tomography (CT) scanning was used to evaluate the performance of diverting agents in real time in rock-fluid interactions. A special aluminum cell (physical simulator) was designed to simulate as accurately as possible the same conditions found in a real oil well. For example, pressure, temperature, fluid pressure injection, permeability, porosity and oil and water saturations of the studied reservoir. A sequence of tests that was performed in the unconsolidated sandstones that simulate deepwater fields found in Campos Basin, in different formations, confirmed the efficiency of the system, its effectiveness and the diverting effect for permeabilities up to 3 Darcy.