Many wells producing medium or heavy oil from unconsolidated sandstone reservoirs experience high water production while still at relatively low recoveries. Water production causes numerous operational problems leading to increased operating and capital expenditures for higher volume artificial lift systems and water handling facilities. The recent development of Downhole Oil/Water Separation (DHOWS) systems has provided operators with an alternative approach to contend with increased water production to improve recovery from these reservoirs.
PanCanadian Petroleum Ltd. has been an industry leader in the development and application of DHOWS technology, particularly with respect to its use in fields producing heavy oil. The use of DHOWS systems in such applications is complicated by the inherent production of sand with the viscous heavy oil. In the commercially available DHOWS systems, the solids that are produced tend to remain in the disposal water stream, which is reinjected downhole. Depending on the solids volume and well conditions, the solids may invade and plug the disposal zone or they may accumulate in the wellbore. In either case, these situations ultimately lead to a reduction in injectivity that reduces the effectiveness, or preclude the further use of a DHOWS system. This decline in injectivity has been observed in field trials with both progressing cavity pump (PCP) and electric submersible pump (ESP) DHOWS systems at PanCanadian's Hayter and Provost fields in northeastern Alberta, Canada (Figure 1). The accumulation of sand in the wellbore was confirmed during subsequent workovers.
PanCanadian enlisted C-FER Technologies Inc. to develop a desanding separator unit for use in conjunction with the commercially available DHOWS systems. A desanding separator unit was designed to remove solids from the produced fluids and to commingle them with the concentrate oil stream produced to surface by the DHOWS system. Following a feasibility study that examined several different design options, a prototype desanding separator was built. The functionality of the separator unit was confirmed through controlled laboratory tests and the unit was subsequently tested in combination with a PCP-DHOWS system. 'The system was then installed in a PanCanadian well which had previously experienced injectivity problems with a DHOWS system. Initial results show that sand is being produced to surface and that the injectivity has remained relatively stable.
This paper describes the prototype system developed and presents the results of the field trial conducted by PanCanadian.
Author: Danyluk, T. L., Chachula, R. C., & Solanki, S. C.
Publisher: SPE Annual Technical Conference and Exhibition, 27-30 September, New Orleans, Louisiana
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