Performance Evaluation and Challenges Using Open Hole Multistage Fracturing Completion to Develop Tight Gas Reservoirs in Saudi Arabia

Abstract

A low permeability gas condensate carbonate reservoir in the Khuff formation is one of the main producing reservoirs in Field-A in Saudi Arabia. This early Triassic carbonate reservoir, first discovered in 1980, holds significant gas-in-place but is a blend of conventional and tight intervals. Vertical completions, horizontal wells with maximum reservoir contacts, and acid stimulation (matrix and fracturing) are some of the current practices to effectively develop the reserves from the tighter intervals. In late 2009, the open hole horizontal multistage fracturing (OHMSF) completion assemblies were deployed in several horizontal wells in the tight gas area with the goal of achieving multiple independent hydraulic fractures, greater acid stimulation efficiency, and thereby enhancing well productivity. The OHMSF systems enable the open hole section to be divided into segments based on the reservoir's petrophysical and flow properties by the use of mechanical open hole isolation packers and customizing the stimulation treatment for each segment via fracturing ports that are installed in between the packer assemblies. Since the inception of OHMFS, many wells were treated and varying results were obtained. The results are dependent not only on reservoir quality and development, but also on the placement of the fracturing ports, number of fracture stages conducted, and fracturing strategy. This paper provides insight into the planning, challenges encountered, sensitivity analysis and performance analysis of the OHMSF wells in comparison with non-OHMSF wells. It also details several case histories and highlights the results as well as lessons learned that can be applied in the future to improve the recovery.