In the oil and gas industry, loss of circulation while drilling is a common problem. Lost drilling fluids typically go into fractures induced by excessive mud pressures, into pre-existing open fractures, or into large openings with structural strength in the formation. Loss of circulation can be costly and difficult to control. Severe losses can disrupt drilling operations for days. A wide variety of materials have been used or proposed [for patents] in attempts to cure lost circulation.1-5 

One of many lost-circulation materials (LCM) used by drilling fluid companies is a super absorbent polymer (SAP). Crosslinked polyacrylamides, polyacrylate, or a combination of both are examples. These SAPs can be used alone or in combinations with other LCM to stop the fluid loss.6-9  SAPs function as LCM by expanding many times in volume when they encounter the fluids downhole and stop the fluid loss by plugging the fractures in formation. These SAPs have shown excellent technical performance; however, they have poor biodegradability, often less than 5% in 28 days (Organization for Economic Co-Operation and Development [OECD 306] Test for Biodegradability in Sea Water). Consequently, there are strong demands from both the regulatory and economic perspectives to develop more environmental friendly LCM to be used offshore.

The ideal LCM for offshore should be formulated with seawater and pose little or no risk to the marine environment, so that after the job is completed, the used LCM can be disposed of overboard. To achieve these goals, research is needed to develop an environmentally acceptable alternative. In this paper we report the results using a biodegradable super absorbent alternative as LCM. Our efforts include studies to further understand the key roles of absorption rate, efficiency and particle size in LCM. Experiments focused on the performance of candidate materials over wide ranges of temperature, pH, and salinity, and also their biodegradation and toxicity performance.

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