Hydraulic fracturing operations in West Africa are not as common as in the US, Latin America and the Middle East. In the Republic of Congo fracturing technology is spreading and has overcome more than few difficulties since the practice began. The most significant challenge has been the formation, which has shown through laboratory testing to be soft and watersensitive. The fracturing project started in the laboratories, identifying critical issues, such as formation heterogeneity, hardness, water sensitivity, clay content and particularly the risk of proppant embedment. The fracturing fluid chosen for the project was a water-based, borate-crosslinked guar fluid, with specific chemicals added to minimize formation softening and clay swelling issues. A specific pumping strategy was implemented when using waterbased fracturing fluid to limit the effects of proppant embedment. Several wells were treated with this system. In an effort to improve well productivity, a pilot test was designed with oil-based fracturing fluid. This fluid was pumped in two wells, resulting in improvements in terms of cleanup time and economics, compared to the water-based treatment fluids in the same field. Part of the economic benefit was gained because of the reduced hydrostatic head of the oil-based fracturing fluid, which eliminated the need for a coiled tubing gas lifting operation. Economics were also improved by minimizing rentals of well cleanup equipment because the broken fracturing fluid can be sent directly to production facilities. In this paper, design and application results for the oil-based fracturing fluid operations are presented with all the operational and logistical challenges overcome.


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