As improved oil recovery activities increases in a field, premature break-through of injected water/gas continue to pose conformance control challenges in reservoir managment. A proactive conformance program is required to address rapid increase of water-oil and/or gas-oil ratios, maintain an effective sweep efficiency and minimize the risk of loss of containment to name a few. The purpose of the Central Permian Conformance Project (CPCP) team was to objectively evaluate the past conformance treatments, causes of their successes or failures, and implement lessons learned to identify possible solutions which improve oil recovery in MCBU's Central Permian assets.

The fields analyzed were clastic and carbonate reservoirs. Both fields provided unique sets of challenges and solutions. Production in the clastic field is from multilayer zones while in the other reservoir there are no distinctive zone separations. The conformance issues in these fields are due to highly permeable layers, extensive fracture networks or vugs.

The Central Permian Conformance Project was divided into three phases: 1) Performed lookback analysis on previous conformance jobs; 2) Use standardized workflows to identify existing conformance issues and solutions; and 3) piloting or fieldwide implementation. This paper focus on part one as the other two phases will be discussed in future publication.

The main focus of this analysis was phase 1 involving lookback analysis of previous conformance control jobs performed. From 1980 to 2013, there were a total of 110 patterns where conformance controls were executed primarily utilizing MARCITSM gel. To have an objective definition of success or failure, a Spotfire® dashboard was created to systematically compare incremental oil production and decline rates before (6 months prior) and after (24 months succeeding) a conformance job.

Lookback analysis on clastic and carbonate fields indicated:

  1. Numbers of successful jobs are meaningfully higher in fractured areas compared to less-fractures areas in analyzed fields

  2. Low success rates occurred mainly in the more homogenous area or where major fractures are absent, and/or permeability contrast is low

  3. A successful conformance improvement is dependent on correct identification of the problem, usage of the appropriate gel, proper placement and slug size as well as a proactive surveillance plan

  4. Other chemicals, such as CO2 foam gel and cross-linked polymers were also evaluated and showed promising results

Based on the lookback analysis, this paper will discuss the systematic data driven approach to evaluate incremental gain or loss of production and use lessons learned to address and emphasize on a systematic approach to select pattern and zone, chemical used and proper designed volume.

Keywords:
flow in porous media, conformance improvement, enhanced recovery, conformance lookback analysis, reduction, MARCIT SM gel, new perspective, central permian conformance project, reservoir, Fluid Dynamics
Subjects:
Reservoir Fluid Dynamics, Improved and Enhanced Recovery, Flow in porous media, Conformance improvement
Copyright 2015, Society of Petroleum Engineers
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