Abstract

Senlac/Winter horizontal well performance is characterized by a short period of high-oil-cut production followed by water cut increases over a several month period to very high water cuts. Previously the more viscous high-oil-cut fluids have typically been trucked to more distant treating facilities, while the subsequent high-water-cut fluids have been pipelined. This project was initiated to field test the feasibility of a novel method of transporting early-life high-oil-cut fluids using high-water-cut fluids from mature wells as the push water, thereby reducing capital costs, operating costs, and environmental risk. The push water system worked well, indicating that Senlac area development can be considered for areas more distant from facilities. Further, when the produced water cuts increased sufficiently to be pipelined without push water, the push water source line was reversed and is now being used to enhance the capacity to carry produced fluids from the new well area to the treating facilities.

This paper discusses the design and operation of the push water system. Also discussed is the phenomenon of core annular flow of heavy oil/produced water mixtures, which may be spontaneously occurring at the conditions in the Senlac Push Line.

Introduction
Problem: Transport of Early Well Life High-Oil- Cut Produced Fluids

Viscous high-oil-cut fluids produced during the early life of outlying Senlac/Winter area Dina/Cummings formation horizontal wells have typically been transported to batteries using trucks. This fluid transport method requires (1) construction of a tank farm with secondary containment, fuel, and flaring, (2) increased requirements for lease road construction and maintenance, and (3) associated increased truck traffic and dust.

When two new well pads were drilled 6.45 km from the closest battery, the decision was made to evaluate alternate methods of transportation. One option under consideration was construction of satellite batteries and water disposal facilities near new well pads, resulting in shipment of relatively dry oil. A second option was installation of a larger pipeline (viz. 10 inch) operated during the high oil cut period by mixing diluent with the produced oil. The third option to trucking was construction of a pipeline system using produced fluids from mature wells as push water during the early highoil- cut period of the new pad wells.

Economic Comparison of Transportation Options

Economic incentive for the dual push water system was greatly driven by the higher cost and environmental impacts associated with the three available alternative methods of transporting produced fluids during the earlywell- life low-water-cut period seen at Senlac wells.

For this project, direct trucking costs were estimated by multiplying the number of new wells (16) by the expected m3/d of production by the trucking cost/m3 by the number of days trucking would be required. The estimated cost is 16 wells × 40m3/d/well × $4.60/m3 shipped by 365 days × 0.95 availability factor = $ 1 MM. Other costs associated with fluid trucking that would not be incurred with a push water system include better roads, more road maintenance, a temporary tank farm incorporating a larger lease to meet equipment spacing requirements, tanks, lease containment, fuel source for the tanks, and a flare system.

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