Research on the possibility of using loading materials to support the treatment of reservoir waters

Abstract

The article presents the issues related to of the removal of suspensions and sediments from reservoir waters. In the conducted research, particular emphasis was placed on the techniques of using loading materials in the water treatment process. The research materials were four types of reservoir water, which was collected from the separators of wells exploiting natural gas deposits. These waters were characterized by high suspended solids (76–176 mg/dm3) and a varied degree of mineralization. The content of dissolved substances was determined in the range from 401 to 306 428 mg/dm3. The extracted reservoir waters are currently most often utilized by pumping into the absorbing horizons in depleted hydrocarbon reservoirs. The preparation of water for injection is limited only to the removal of easily settling solid particles and suspensions present in the extracted formation waters. The porosity and permeability of the deposit rocks determine the size of solid particles present in the water that can be forced into voids in the porous medium. In the process of water treatment by coagulation and flocculation, carried out in laboratory conditions, Flokor ASW was used as a coagulant, while Stabpol was used as a flocculant. Post-coagulation sludge is highly hydrated, so that its density is close to that of water, as a result of which sedimentation of sludge particles takes a long time. In order to increase the sedimentation rate of particles contained in the treated waters, ballasting materials, which were quartz sand and bentonites: powdery bentonite and bentonite preparation DuoBent 1, were successively introduced into the solutions. The effectiveness of the water treatment process was assessed by comparing the degree of turbidity of the solution above the sediment before and after adding a different amount of coagulant, flocculant and sediment-balancing materials. The turbidity measurement of the tested solutions allows to estimate the content of suspensions and colloids in them. Laboratory tests were carried out on the possibility of using selected materials ballasting suspensions in the process of reservoir water treatment. Effective doses of ballast materials recommended for use in the separation of suspensions from formation waters were determined. Research results presented in this paper show that the removal of suspended solids from formation waters can be carried out with the use of a properly prepared bentonite agent (DuoBent 1) with no need of adding other chemical compounds. The doses of the DuoBent 1 bentonite preparation, dosed into highly mineralized reservoir waters in order to remove turbidity, are relatively small. Adding bentonite into the treated waters in amounts exceeding 0.2 g/dm3 results in obtaining high clarity of the water intended for injection (turbidity at the level of 0–5 FAU). The results of the research can be implemented for practical use as a simple method of purifying reservoir water prior to injection into the formation.