Key factors in framing a produced water management (PWM) strategy include a company's internal and external environments, technology, and business drivers. Emerging trends for establishing an environment-friendly PWM position comprise adoption of these policies:
Move toward zero emissions.
No discharge to surface or seas.
Incremental and progressive separation.
Proactive efforts to influence partners, regulators, and environmental laws.
This paper covers technical approaches for addressing the production, separation, and disposal/injection segments of water injection and reservoir waterflooding procedures and the basis for selecting strategy components and PWM actions. Best practices result both from comprehensive assessments of current PWM tools and from the insights obtained from a decade-long joint industry project (JIP) on produced water re-injection (PWRI).
PWRI for waterflooding or disposal is an important strategy for deriving value from waste while preserving environmental integrity during exploration and production (E&P) operations. Advances in best practices and lessons learned for injector design, operation, monitoring, assessment, and intervention provide the basis for cost minimization and green operations. Facility and subsurface engineering are linked through PWM quality targets, pumping needs, injector completions, and facility constraints. Field cases and data mining results (Abou-Sayed et al.2005) show the variation in injector responses and underline the key elements contributing to performance. Field evidence indicates that injectivities suffer in matrix injection schemes despite the injection of clean water. Alternatively, injectivity maintenance using untreated produced water is feasible.
The majority of injectors fracture during injection, thereby impacting facilities' statement of requirement (SOR), injector completion, sweep, and vertical conformance. This paper assesses fracture propagation during seawater and produced water injection and its impact on injector performance. Models depicting plugging of formations and fractures, vertical water partitioning, and well testing are discussed. Best practices are highlighted and the impacts on injection strategy outlined. Several field cases, as well as water injection design and analysis tools for quantifying the impact on flood and well performance, are presented.
PWRI technology application for oilfield management has been steadily increasing over the last decade in various parts of the world (Sirilumpen and Meyer 2002; Van den Hoek et al.2002; Furtado et al. 2005; Hjelmas et al. 1996). Successful injection operations have been reported by operators in the North Slope of Alaska, the west coast of Africa, and the North Sea. PWRI offers the dual benefit of disposal of oil-filled waste water and solids in an environmentally safe way and enhanced hydrocarbon recovery by improving reservoir fluid sweep and pressure maintenance. The successful application of this technology in the oil field does not depend only on the disposal of solids/contaminants, but also on the maintenance of injectivity for effective sweep and injection conformance for improved recovery.
This paper discusses the physical phenomena, namely matrix and fractured injection, involved in PWRI and the associated issues with regard to injectivity and facility requirements. A fracture plugging and propagation model is presented to explain the cyclic injection pressure behavior observed in some injectors. Thermal fracturing can allow fracture containment and reduce injection system requirements. Field cases clearly showing the effect of injection water temperature on fracture pressure and injectivity are discussed. The knowledge gained from the JIP is used to establish guidelines and best practices for implementing a PWM strategy.