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Artificial Lift Techbook 2018

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EPmag.com | July 2018 | 47 ARTIFICIAL LIFT: CASE STUDIES unchecked scale buildup, high pressure or motor overheating can cause the ESP controller to shut down the well to protect the system. In a scale-prone field in the Egyptian West Des- ert, Khalda Petroleum Co. used the production life-cycle management service to detect early scale buildup on an ESP in one of its artificially lifted wells and recommended immediate action to rem - edy the situation. When engineers at the Middle East ALSC recognized a rise in intake pressure and motor temperature as an early sign of the scale buildup, they recommended decreasing the motor loading to prevent the well from tripping. This action enabled the onsite Schlumberger team of field engineers to clear the scale by safely inject- ing acid washes through coiled tubing directly on the discharge head of the pump. Without the acid treatment, the motor likely would have continued to overheat, resulting in reduced runlife or cata- strophic failure (Figure 1). Early detection of the scale buildup and quick response to address the problem prevented unnec- essary delays and saved Khalda Petroleum $540,000 in workover costs and deferred production. Eliminating costly workovers In a North Sea field, scale buildup resulted in slow production in affected wells, forcing the operator to perform scale squeeze treatments by pumping an inhibitor downhole to prevent scale deposition. Over a period of several years, the operator per- formed 630 scale squeezes on 50 wells in the field, 10 of which experienced ESP failures within one month of the treatment. Each failure required a $2 million workover. Upon investigating the problem from a center in the U.K., the DIFA team determined that 10 ESPs have experienced electrical failures immediately following the scale squeeze treatments. The failures were triggered by the fluid treatment ingress past FIGURE 1. The Khalda Petroleum Co. well experienced partial plugging due to scale deposition. The issue was ident ified, and an acid wash was performed. However, the Lift IQ service showed that motor temperature continued to rise after the acid wash, so the ESP speed was remotely reduced to lower the temperature. ( Image courtesy of Schlumberger)

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