In-depth Sweep Efficiency Improvement: Screening Criteria and Engineering Approach for Pattern Evaluation and Potential Field Implementation

Abstract

Abstract A common problem of waterflooded oil reservoirs is the premature water breakthrough bypassing high remaining oil saturation in unswept zones that are risky targets for infill and sidetrack drilling. Early water breakthrough can be caused by reservoir heterogeneity and unfavorable mobility ratios of oil and injected water. There are several IOR/EOR technologies that can be used to reduce water production and increase sweep efficiency. Polymer gels ("Conformance treatments"), polymer flooding and Colloidal Dispersion Gels (CDG) are some of the technologies most commonly used during the last few decades. However, the applicability of a given technology will depend on the problem (e.g., water channeling, adverse mobility, etc.) and its applicability under given reservoir conditions (e.g., temperature, salinity, lithology, and injection and fracturing pressures, among others). The purpose of this paper is to describe screening criteria for thermally-activated polymer (TAP) flooding technology implementation before starting detailed project evaluations. Based on the suggested screening criteria and evaluation approach, it is possible to rank patterns or asset candidates for in-depth conformance treatments to improve sweep efficiency or delay premature water breakthrough. This is especially important for projects in remote areas or in offshore conditions where water handling is costly. Based on field experiences, laboratory experiments, and new simulation approaches that are being continually improved, in-depth conformance treatments are carefully designed before pilot or asset implementation. The proposed screening methodology was used to evaluate and rank temperature-triggered polymer applicability in more than 20 Russian oil fields. Results show how to identify good or poor candidates to evaluate the technology, which increases the probability for successful implementation. In some other instances the combination of technologies might be required to maximize ultimate recoveries.