Shale oil companies are currently building state-of-the-art gathering infrastructure to transport oil and natural gas from the wells through an oil gathering system to a central oil stabilization facility to eliminate truck traffic and condensate tank emissions. A portion of fracturing fluids and sand that returns to the surface (slickwater and proppant backflow) may accumulate in this new-built pipeline infrastructure and cause severe pitting corrosion. Also, paraffin and wax deposits may cause operational problems in various parts of the oil gathering system. In offshore production systems, production streams frequently contain organic/inorganic solids and water causing corrosion and wax buildup in subsea pipelines, which are unpiggable in many cases.
We propose a novel system for removing solids, wax, sludge, and other unwanted fluids causing corrosion and/or flow assurance issues in oil and gas gathering systems, including manifolds and unpiggable process lines. The system comprises one component that generate fluid batches at the inlet of the flowlines and a model-based controller component that determines the launch time of fluid batches such that the batches generated in the flowlines are merged into one batch in the gathering pipeline or production manifold. The controller simulates the fluid batches moving along the flowlines using a real-time simulation model and provides automatic control of the systems generating the fluid batches. The dose of corrosion or wax inhibitors is automatically adjusted to maintain a predetermined concentration of the chemical in response to a variation of the rate of water production in the well.
Scale-model test results and real-time simulations of system operation are presented. The stationary bed of solids formed in the production manifold and process lines is converted into a series of solids dunes that slowly move toward the separator. This effect dramatically reduces the likelihood of internal corrosion. Also, the risk of wax deposition reduces because the internal surface of the pipe is continuously flushed by hot water batches. This technology is applicable for existing and new-build pipeline infrastructure and virtually does not have limitations regarding the design of the oil or gas gathering system, operating pressure and temperature. As a result, the production manifold itself and unpiggable process lines are efficiently flushed with produced water.