Evaluating water injection compatibility and scale-formation reduction in a middle east reservoir using direct pore-scale visualization and NaOH treatment

Water injection into a reservoir is a necessary process throughout the reservoir's lifespan. However, it can lead to certain side effects, such as scale precipitation in production wells and surface facilities due to water incompatibility. This can result in damage to the well, reservoir, and ultimately a decline in production which happened in one of the west of Karoon's reservoirs and caused the well lost. For solving this problem this case study was conducted with the brine of the reservoir in the reservoir temperature (120 °C) and different economical water samples for water injection. When water combines with the formation water, it can form sediments that cause incompatibility, leading to the precipitation of inorganic scale deposits in surface facilities, flow lines, wells, and even the reservoir itself. Therefore, it is crucial to design the injected water to minimize incompatibility. To address this issue, water compatibility tests should be conducted on the water samples to prevent scale precipitation and ensure successful water injection. In order to investigate this phenomenon, experiments were carried out in both dynamic and static phases. Water samples from the lagoon, mineral water, and synthetic water were mixed with formation water at different temperatures and mixing ratios in static tests. The results indicate that synthetic water (S) was generally incompatible with formation water in most experiments. While mineral water (M) showed compatibility in some mixing ratios and temperatures, lagoon water (L) demonstrated greater compatibility with formation water compared to M water. In cases where M water showed better compatibility, the difference in scale formation between L water and M water was negligible. Based on the availability and the results of this research, L water was chosen as the more compatible water among the three selected samples. Subsequently, tests were conducted using lagoon water and formation water. A glass micromodel with a designed pattern was utilized to observe scaling formation and distribution easily. Photos captured through fluorescent scanning, along with a MATLAB code developed to determine the percentage of reduced porosity, revealed that approximately half of the pores were plugged. To address this reduced porosity, a novel technology involving the use of NaOH in a static situation (jar test) was employed. The jar test was conducted at four different temperatures near the reservoir and well's temperature (120 °C, 95 °C, 85 °C, and 75 °C) with two percent mixing of lagoon water in contact with the formation water of this case study. These tests were repeated under the same conditions but with the addition of NaOH to the mixing water. The results of this innovative technology showed promising outcomes, as the weight of scales was reduced, and scanning electron microscope (SEM) analysis revealed a transformation to more soluble scales both in dynamic and static tests.