Progressive Cavity Pumping is the preferred artificial lift method in the extra heavy crude oil field Huyapari, located in the Venezuelan Orinoco belt. Typically, PCPs operating in saturated reservoirs such as Huyapari need to cope with significant amounts of free gas, often handling more than 50% of gas void fraction (GVF) at the pump intake. This, combined with production of large amounts of sand and exposure to aggressive fluids, poses vast challenges to the durability and performance of PCP elastomers. Consequently, a proper and engineered selection of elastomer materials has critical impact on overall pump run life.

This study describes a first experience in characterizing the effect of harsh fluids and solids on high acrylonitrile elastomers. Subject wells include those with high free gas and/or sand production rates, as well as those with elevated water cuts. The mechanical properties of elastomers were measured under controlled pressure and temperature conditions in order to define an optimum rotor-stator fit. Over 200 laboratory tests and several field experiments were conducted to allow for the most suitable selection of elastomer material regarding hardness and swelling behaviour. Aging tests and infrared spectroscopy were also used in these analyses to help reduce premature elastomer failures produced by hysteresis, explosive decompression and blistering. The results of the study indicate that PCP applications in wells producing high gas rates must avoid utilization of elastomers with a hardness below 65 shore A, because the increased gas permeability causes excessive swelling throughout the pump stator. In contrast, elastomers with hardness above 70-75 shore A proved to be more resistant to swelling and explosive decompression.

Benefits resulting from this study include an increased pump life cycle from 306 days in-hole in 2012 to 469 days in 2016. Premature PCP failure count decreased from 275 in 2012 (59% of wells in the field) to 153 in 2017.

Based on the results of this study, the authors propose new acceptance ranges for mechanical properties values (e.g. swelling performance and hardness) for PCP elastomer selection applied to extra heavy oil production in this field.

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