Multiple Transverse Fracturing in Open Hole Enables Development of a Low-Permeability Reservoir
Authors: Denney Dennis 
Published: February 2015

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 119140, "Multiple Transverse Fracturing in Open Hole Allows Development of a Low-Permeability Reser voir in the Foukanda Field, Offshore Congo," by Alberto Casero, SPE, Loris Tealdi, SPE, Roberto Luis Ceccarelli, SPE, Antonio Ciuca, SPE, Giamberardino Pace, SPE, Eni; Brad Malone, SPE, Schlumberger; and Jim Athans, SPE, Packers Plus Energy Services, prepared for the 2009 SPE Hydraulic Fracturing Technology Conference, The Woodlands, Texas, 19–21 January. The paper has not been peer reviewed.
During the past decade, multiple transverse fracturing in horizontal wells has been applied successfully in onshore low-permeability reservoirs. The reasons for the success of this technique are related to the effectiveness of hydraulic fracturing for production enhancement and to the relatively low cost of pumping services onshore. Offshore, high direct and indirect costs and the risks associated with operations have limited the use of this technology. This study documents the successful effort of taking these techniques offshore. Transverse fracturing with multistage completion—with properly engineered design of the well trajectory—can provide economic success of field development of low-permeability reservoirs.

Introduction
The Foukanda marine field is 20 km north of the Kitina platform and 52 km west of the city of Pointe Noire, Congo. Average water depth is 100 m. The field was discovered in 1998, with initial production in June 2001. That year, one well was drilled in the D reservoir, but it had very poor reservoir characteristics, and this level was abandoned. The well was recompleted in the shallower B4 reservoir. The low-permeability D reservoir (less than 10 md) was abandoned.
Successful fracture treatments in the Kitina field in May 2007 proved the possibility of obtaining economical rates from a marginal reservoir. It was decided to test the multistage hydraulic-fracturing technology on the previously abandoned D reservoir in the Foukanda field.
Synergy from early cooperation among drilling, reservoir, and production-enhancement engineers proved key for the operation. An optimum process path was followed: reservoir assessment, selecting optimum fracture(s) configuration, providing input for the drilling plan, selecting the proper completion to allow optimum fracture(s) placement, and, finally, plan execution.
The original plan on Foukanda was to drill a new vertical or deviated well with one or two fractures. Fracturing engineers suggested changing this plan and drilling a horizontal well and completing it with multiple transverse fractures. The deviated well was discarded because of complex fracture-growing issues, which, in the best case, could have transverse fractures that are not properly spaced, resulting in fracture/production interference. The advantage of having transverse fractures in a horizontal well is the possibility of proper spacing and deciding the optimum number of fractures that are required.