The Analysis of Chemical Processes in Reservoirs Based on the Identification of Injection Water Fraction in Produced Brine

摘要

The time and subsequent evolution of injection water breakthrough are some of the main indicators production chemists monitor for. After injected water breaks through, the risk of scaling may significantly change and scale mitigation procedures should be planned accordingly. The fraction of the injection water in the produced brine may only be ascertained from analysis of the produced water samples. So far, however, there has been little discussion about other applications of injection water fraction tracking. In this paper new applications that follow on from accurate knowledge of injection water fraction are proposed. The calculated injection water fraction may be applied to: 1. Quickly and accurately identify when injection water breakthrough has taken place and therefore remedial action to prevent scale damage needs to be implemented. 2. Identify which ions are involved in in situ geochemical reactions, and the degree of relative ion deviations; identify ion exchange reactions (Relative Ions Deviations). 3. Detect which formation or formations a well is producing from, and potentially the amount of flow from each layer without the use of downhole flow metering. Strong evidence of the involvement of barium, sulphate, and magnesium ions in reactions, based on the calculations of the Relative Ions Deviations, has been shown for field data. In another case, application of injection water fraction prompted a re-evaluation of the formation water compositions, and as a result it was discovered that the well was producing from a different formation after re-perforation. The significant new developments presented in this paper allow analysts to obtain an indication of which ions are involved in the reactions, and the degree of relative ion deviations. Additionally, a technique which identifies which formation or formations the well is producing from is proposed.