Generalities – Water Shut-Off & Conformance
Generalities on Water Shut-Off & Conformance. Excess water production is a persistent challenge in oilfield operations, leading to increased operational costs, reduced oil recovery efficiency, and environmental concerns. Water shut-off and conformance improvement are critical strategies employed to address these issues and enhance the overall performance of mature and heterogeneous reservoirs.
This section introduces the fundamentals of water shut-off and conformance control, drawing on decades of field experience and scientific research. One of the most referenced works in this field is by Seright and Brattekas (2021), who outline a practical approach to identifying, diagnosing, and treating water production problems. The classification of problem types, from channeling through fractures to excessive matrix flow, helps operators select appropriate solutions—ranging from mechanical isolation to chemical gel treatments.
A key concept explored is disproportionate permeability reduction (DPR), where polymer and gel systems selectively reduce water flow more than oil or gas. This phenomenon is especially useful in treating conformance issues in fractured zones, as explained through detailed studies on gel behavior and efficiency during and after placement.
Further insights are provided into in-depth profile modification, an advanced method of selectively blocking high-permeability zones to redirect flow and improve sweep efficiency. Comparative studies show when this method is more suitable than conventional polymer flooding, particularly in reservoirs with strong permeability contrasts.
Through this curated content, readers will gain a comprehensive understanding of the mechanisms, technologies, and strategic decision-making involved in water shut-off and conformance improvement. Whether you are a reservoir engineer, production specialist, or EOR researcher, this page offers valuable technical insights and references to guide practical applications in the field.
Explore the articles to deepen your knowledge of chemical water control, polymer gels, fracture sealing, and conformance optimization in oil recovery.
Table of Contents
This paper describes a strategy for diagnosing and solving excess water production problems — advocating that the easiest problems be attacked first and that diagnosis begin with information already at hand. A ranked listing of water production problem types is provided, along with their relative ease of solution. The major focus is when and where gels can be effectively applied for water shutoff. Problem types are organized into categories ranging from Category A (conventional treatments — cement, mechanical devices — normally effective) through Category D (problems that gels typically cannot solve, such as 3D coning). For each problem type, the appropriate class of technology is identified. The paper emphasizes that many operators skip diagnosis, leading to poor treatment success rates, and provides a cost-effective methodology for correct problem identification before treatment selection.
This paper investigates when in-depth profile modification (using a blocking agent that places a deep plug in the high-permeability zone) is superior to conventional polymer flooding for stratified reservoirs with free crossflow. Using simulation and analytical studies, oil-recovery efficiency was examined as a function of permeability contrast, relative zone thickness, oil viscosity, polymer-solution viscosity, bank size, and relative costs. In-depth profile modification is most appropriate for high permeability contrasts (10:1), high thickness ratios (less-permeable zones 10 times thicker than high-permeability zones), and relatively low oil viscosities. Because of the high cost of the blocking agent relative to conventional polymer, economics favor small blocking-agent-bank sizes (e.g., 5% of high-permeability pore volume). Even though short-term economics may favor in-depth profile modification, ultimate recovery may be considerably less than from a traditional polymer flood. In radial flow, polymer flooding gains a relative advantage over in-depth profile modification compared with linear flow.
This review paper provides an introduction to water shutoff and conformance improvement. After indicating the volumes of water produced during oilfield operations, a strategy is provided for attacking excess water production problems. Problem types are categorized, typical diagnosis methods are mentioned, and the range of solutions is introduced for each problem type. The concept of disproportionate permeability reduction is introduced — where polymers and gels may reduce permeability to water more than to oil or gas. The properties of formed gels as they extrude through fractures are described and related to treating conformance problems caused by fractures. The efficiency with which gels block fractures after placement is covered, including the impact of fluids injected subsequent to the gel treatment.
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