A Systematic Laboratory Core and Fluid Analysis Program for the Design of a Cost Effective Treatment and Cleanup Guidelines for a Produced Water Disposal Scheme

Abstract

Abstract A practical and systematic technique for the determination of cleanup guidelines based on laboratory rock and fluid studies is presented. This method was employed in the preliminary design of a water disposal scheme requiring a high rate (30,000 bpd per well) into a shallow aquifer system in the Niger Delta. A description of the laboratory tests employed in the evaluation of the potential and the degree of impairment from the different mechanisms is presented along with interpretations and scaling of laboratory data to field operating conditions. Injectivity impairment resulting from relative permeability effects due to increased oil saturation over time, emulsion block, particulate plugging from suspended solids and in-situ mobilization, and clay swelling were quantified by time dependent pseudo skin factors. A composite time dependent pseudo skin was derived from the combination of the individual components obtained from specially designed laboratory analytical tests on representative core and fluid samples. The results were extrapolated to field conditions using standard scaling techniques and employed as a basis to determine water treatment requirement and periodic cleanup guidelines. This approach enabled the conceptual design of a pilot water disposal scheme based solely on laboratory study of representative produced water, formation water and aquifer rock samples. Specification for water clarification, filtration, formation pre-treatment guidelines and cleanup schedule for the disposal well in the target aquifer system were made apriori to field implementation. Introduction The quality of the source water (produced or surface) is of prime concern in any water injection or disposal project. Clean water is particularly important in wells requiring sustained injection at high rates. Oil and suspended solids must be held to a concentration below maximum tolerable limits to maintain injectivity for an extended period of time. The objective of this water disposal study was to assess the feasibility of subsurface disposal of produced water from an inland dehydration station. The study was based on the current need to dispose of 175,000 bbl/d and the possible future need to dispose of up to 300,000 barrels per day of produced salt water by the year 2008. The following four major tasks were pursued in the study;Identification of candidate aquifer system(s) for the disposal of the produced waterCharacterization of the aquifer system, compatibility studies, and development of injectivity criteria P. 245