Fracturing a Tight Sand Formation with High Frac Gradient Onshore Saudi: Challenges and Solutions

Abstract

Abstract Saudi Aramco has recently embarked on an exploration program targeting unconventional gas reservoirs to meet the ever increasing local gas demand. One of the targets is a tight sandstone play located to the east of a giant hydrocarbon reservoir with limited reservoir data through the few exploratory wells drilled in that play. The target formation is considered a deep reservoir with very low permeability and high fracture gradient. In order to evaluate the potential of the subject formation, wells have to be completed with a hydraulic fracture. Given the challenging nature of the reservoir in terms of stress, pressure and temperature, a sophisticated design of both well completion and fracturing treatment must be performed to successfully evaluate the potential of those wells. This paper highlights all the challenges encountered and overcome from completing to fracture stimulating one of the wells in the target tight sandstone formation. Among the challenges is dealing with the completion limitation in terms of the maximum allowable pressure during the fracturing operations. Detailed simulations of the stress and thermal conditions mimicking the fracturing treatment have been analyzed to maintain the integrity of the well during the stimulation operations. Another challenge is the high fracture gradient and high closure pressure which resulted in limiting the injection rate to place the proppant. A cost effective fracture fluid formulation has been adopted to be able to frac and place the proppant without exceeding the tubing maximum allowable injection pressure. The fluid used was a linear gelled fluid system consisting of heavy brine which was selected after extensive laboratory testing. Acid spearhead along with sand slug was also employed to overcome the high NWB (Near Wellbore) friction and the proppant was placed successfully. This paper presents a step-by-step design process which could be applied by other engineers to help in placing proppant into challenging formations with similar attributes of the subject formation.