Transient Multiphase-Flow Simulation Enables Slugging Mitigation Solution

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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 195740, “Long Cyclic Well-Slugging Behavior Induced by Sand Production; Analysis and Mitigation Solution Enabled by Transient Multiphase-Flow Simulation,” by Kapil Kumar Thakur, SPE, Schlumberger; Kia Katoozi, SPE, TAQA Bratani; and Ali Hamid, SPE, Schlumberger, prepared for the 2019 SPE Offshore Europe Conference and Exhibition, Aberdeen, 3-6 September. The paper has not been peer reviewed. The complete paper discuses a well with a history of sand production that exhibits long cyclic slugging behavior. Whether the slugging is caused by the gap at the well’s lower completion, by sand transportation, or by both is not fully understood. Dynamic wellbore modeling with sand-particle transport is essential in modeling the complex slugging behavior. Transient simulations successfully produced the slugging behavior observed in the field. Cyclic slugging was determined to be caused by the flow dynamics generated by particles of small to medium size. Introduction Well X1 exhibited long cyclic slugging behavior, as seen from the tubinghead pressure (THP) and downhole pressure measured for 1 month (i.e., 0 to 30 days) (Fig. 1). Surface rate measurements from the rate test are available for 1 week (i.e., from Days 23 to 30); these are shown in Fig. 1 along with downhole pressure. For this period, downhole pressure decline is observed as the rate builds. The objective of this analysis is to understand the long cyclic slugging behavior of the well by analyzing and simulating historical production data and to arrive at a potential mitigation solution. Wellbore Modeling The multiphase-flow model incorporated in the commercial transient multiphase simulator used in this study is based on first principles whereby the equations of mass, momentum, and energy are solved in time and space to arrive at temporal and spatial variations of phase fractions, velocities, pressure, and temperature. These mass, momentum, and energy equations are solved rigorously in the transient multiphase simulator model with the appropriate closure laws defining interfacial and wall friction, deposition and entrainment of droplets, and bubble entrainment. The model is suited to well-simulation applications because it can simulate complex trajectories, smart completions, and the transient heat transfer in wells by accounting for all the applicable modes of heat transfer (conduction, convection, and radiation) between the tubing, casing, and formation. The model is capable of handling sand-particle transport.