Optimization of Multiple Hydraulic Fractures for Open Hole Horizontal Wells by Numerical Modeling—Saudi Arabia Case Study

Abstract

Technological advances in the use of open hole completion with mechanical isolation have led to the ability to perform multiple fracturing applications in one continuous efficient operation. The new system allows effective hydraulic fracture placement by segmenting the lateral with mechanical isolation points using high-performance open hole packers. This application was used successfully in carbonate plays in Saudi Arabia where multiple acid fracture stimulation improved productivity from seven compartments and anisotropic reservoirs with high productivity contrasts. Optimizing reserve development while maintaining maximum well productivity requires reliable evaluations of stimulation performance for field development planning. Reliable methods include the use of numerical reservoir simulation for the design, in combination with transient analysis techniques for the evaluation of the stimulation solution. In this study, a reservoir simulator incorporating a hydraulic fracture model within a subsurface geological software environment was used to optimize multiple fracturing in an open hole horizontal well in Saudi Arabia. The study investigated the impact of fracture number, location, spacing and geometry on reservoir drainage efficiency by using a sector model with a multisegmented horizontal wellbore model. Comparing various types of reservoirs shows how fracturing design can benefit from understanding the interaction between the reservoir and the horizontal wellbore intersected by hydraulically induced fractures. An actual reservoir simulation model with geological and structural inputs was used to history match the performance of the fractured well. The same model was also used to interpret the transient pressure buildup data through their flow regimes. Introduction A Saudi Aramco oil field, Field Q, is located in the Eastern Province of Saudi Arabia and forms a gently folded north-south trending double anticline that is divided into two structural highs — the north and south domes. The northern tip of the North Dome extends into coastal waters of the Persian Gulf. The target reservoirs for the current field development are the Late Jurassic and Middle Jurassic carbonate formations. Peripheral water injection has been used to maintain reservoir pressure. The water injectors and oil producers are completed with 6 1/8-inch open hole horizontal wells with 3,000 ft to 7,000 ft open hole section. The oil producing wells are drilled typically through layers B1 (most prolific with high perm) B2, B4 and B5 (low perm with marginal contribution).