To Treat or Not To Treat? Optimized Water Decisions Throughout the Produced-Water Management Cycle

Abstract

In the rush to market and sell an approach to treating produced water, there seems to be a distinct lack of understanding of one of the basic questions that must be established before a water treatment solution can be provided: What is the water quality treatment target?The term "produced water" has materialized in the lexicon of the profession of industrial wastewater treatment as the new field of research and opportunity due to hydraulic fracturing and its need for significant water quantities to fracture the formation and during initial flowback or production. In truth, produced water has been managed in increasingly larger volumes in conventional oil and gas (O&G) wells ever since initial production began in the mid-1800s. Only due to the high price of O&G in world markets have the techniques involved in fracturing and enhanced oil recovery (EOR) made economic sense. Both fracturing and EOR require water to be injected into the formation to produce O&G in contrast to the practice in traditional O&G fields where the commingled water, oil, and gas are produced and then separated, and the water is normally either reused in waterflooding, for pressure maintenance, or handled as disposable waste. Due to the more complex chemistry associated with developing fluids for fracturing or EOR, these two enhanced recovery methods and the produced water associated with them have now garnered considerable attention from equipment suppliers, technology providers, engineers, and scientists from outside the mature field of O&G facility engineering.This study focuses on how and why water and wastewater treatment targets are developed and takes them to their ultimate conclusion in terms of economics as to why one could justify the expenditure of treatment as compared to the increases it provides in terms of O&G production. The treatment targets often include a vast array of requirements including meeting environmental regulations; protection of piping and production infrastructure; compatibility with various stimulation fluids from crosslinked gels, viscoelastic fluids, and fibers in fracturing fluids to surfactants, polymers, and foams in chemical and miscible gas EOR floods; prevention of reservoir damage due to fluid-fluid and rock-fluid interactions including souring and reduced permeability due to plugging or scaling; and simple treatment to preserve injection wells or complex scenarios for surface discharge. To develop an optimized water management approach, it is essential to have a complete understanding of the effects that water has on the process thru every phase of the sourcing; treating; conditioning; pumping; downhole operations; production; and reuse, disposal, or treatment for surface discharge. Coupling these needs and effects with an understanding of the costs of treatment enables one to answer the question: To treat or not to treat?