The success of many oilfields depends upon efficient disposal of produced water. In the case of the Masila block in Yemen, the difficulty of water disposal was underestimated because the high permeability of the production wells led to expectations that high injection rates and economic subsurface disposal would be easily attained.
A number of standard approaches were taken to obtain injection rates of 40,000 BWPD per well. After initial failures, a multi-disciplined team was formed to review the practical and theoretical aspects of formation damage and water quality. Successful injection at rates exceeding 80,000 BWPD per well were subsequently achieved by underbalanced drilling and improving water quality. Two orders of magnitude of increase in injectivity index. Optimizing the drilling and completion methods saved S14MMUS that would have been needed to dispose of water at hydraulic fracturing pressures.
The learning curve and dead ends that led to the successful subsurface disposal of over 200,000 BWPD are described. Perforating, core flow tests, core analysis, corrosion, sand behavior, pressure measurement, drilling fluids, completion configuration, filtration and remedial stimulation are discussed.