DOWNHOLE WATER LOOP - A NEW COMPLETION METHOD TO MINIMIZE OIL-WELL PRODUCTION WATERCUT IN BOTTOM-WATER-DRIVE RESERVOIRS

Investigated in this study is a recently invented method to cut back t he volume of formation water produced by an oil well from a hydrocarbo n reservior underlain by a water zone. The method involves initial com pletion of the well inside the water zone, below the oil-water contact (OWC) to install the water loop equipment, which is then separated by a packer from the conventional completion in the oil zone (above the OWC). Below the packer, the water loop installation includes a submers ible pump, the upper perforations (water sink), and the lower perforat ions (water source). The submersible pump drains the formation water a round the well from the water sink, and then reinjects the same water back to the water zone through the distant water source perforations. In principle, the method should increase oil recovery with less (or no ) formation water produced at the wellhead. Also, the method gives sol ution to the environmental problems associated with safe disposal to p roduced water. A simulation study was conducted to investigate the hyd rodynamic performance of the method to restrain water movement towards oil-producing perforations. The downhole water loop was mathematicall y modelled using the flow potential distribution generated by two cons tant-rate sinks (oil and water) and one constant-rate source (water) l ocated between the three liner boundaries and the constant-pressure ou ter radial boundary. The mathematical model was verified using date fr om studies on water coning. A good match was obtained when the distanc e between water source and water sink approached zero. The study revea ls that the shape of the dynamic OWC in the well's vicinity can be eff ectively controlled by the method so that the oil production rates can be two- to four-fold higher than the critical rates obtained when usi ng conventional completions. The method becomes increasingly effective when: (1) the oil production by strong water drive is hindered by wat er coning; (2) the bottom section of the well (in the water zone) is d eviated so that the water source can be set below and aside from the w ater sink; and (3) the water zone is tick enough to allow sufficient l ateral departure of the water loop without excessive curvature of the bottom section of the well.