Wintershall started in 1994 with the preparation of frac treatments. Between 1995 and 2004 eight wells were fractured. Only one frac was conducted in Libya in the mid 1970s and the challenge was to introduce this technology. Firstly, a service company had to be encouraged to provide the equipment, the service and logistics for chemicals and proppant. Secondly, the National Oil Corporation had to be convinced that application of this kind of technology would be feasible and beneficial for the development of a low-permeable reservoir.

All wells in the subject field produce from a heterogeneous Lower Cretaceous Sandstone at a depth of about 12,000 ft. The drive mechanism is solution gas drive since the underlying aquifer was found to be inactive. Low porosities of 10 to 14 % and poor permeability ranging from 0.1 to 20 mD allow only a low to moderate production, which hampers the economics of a field development.

Today, 80% of the production wells in this field have been successfully stimulated by hydraulic frac treatments. State-of-the-art real-time analysis was performed to evaluate and optimize the frac operation on the fly. Hydraulic frac simulation findings were compared to post-frac well test results obtained from pressure buildup analysis in order to crosscheck the outcome.

About half of the cumulative oil produced to date can be assigned to the frac stimulations. However, they did not only help to improve the productivity of each well, but allowed us to produce longer above the bubble point and even permitted an optimization of production with bottomhole flowing pressures below the bubble point. Hydraulic prop fracs have successfully shown to be an appropriate means of reservoir management in this oilfield.

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