Establishing a New Working Ground: Horizontal Multistage Hydraulic Fracturing in Marginal Oil Reservoirs

Abstract Hydraulic fracturing was recently introduced to the Haradh formation to create a conductive pathway in a reservoir characterized by significant vertical and horizontal heterogeneity. This technique improves production rates beyond the economic threshold in both vertical and deviated wells. Due to limited surface locations, developing the reservoir with single-stage vertical wells may not adequately recover reserves within a specific timeframe and could lead to surface facility congestion. Consequently, horizontal multistage fracturing was explored in the fields to increase reservoir contact and enhance production with a minimal number of wells. This project represents the first application of horizontal multistage fracturing in the marginal oil fields of the Haradh formation. A detailed groundwork was conducted to evaluate the feasibility of horizontal multistage fracturing before drilling the well, aiming to bridge the experience gap regarding the impact of this development in the same formation. The evaluation of the horizontal well began with a drilling plan based on the field's 3D reservoir model. This plan considered the field's anti-collision steering, stress direction, and fracture geometry. Multiple hydraulic fracturing design sensitivities were run, respecting the heterogeneity and geological features in the 3D reservoir model, to avoid breaking into the water zone and hitting other wells during execution. Production forecasts, based on fractures created in the reservoir model, were performed using state-of-the-art simulators to evaluate the project's economics and determine the number of stages along the lateral. The execution plan employed the simplest methodology, including plug and perf methods using coiled conveyance to allow mechanical intervention when needed. Chemical tracers were also pumped into the well to evaluate the productivity of each stage, as conventional production logging would not be able to perform in the well. The detailed work conducted prior to drilling the well provided valuable insights into the impact of geological features on fracture geometry and behavior. This allowed the software to generate propagation profiles based on the dip, layers, and lateral positions. It also mitigated the risk of frac hits to other wells and minimized investment risk by providing expected production profiles from the actual reservoir model. Although the execution model did not offer the fastest turnaround time, it effectively supported the necessary mechanical interventions for the well, which could have been problematic without the use of coiled tubing. The deployed surveillance successfully provided production profiles for each stage, both during water flowback and oil production. This paper details the workflow of the first multistage hydraulic fracturing operation in the Haradh formation. It showcases methods to mitigate risks in planning and execution before making the investment. The lessons learned and step-by-step methods shared in this paper will also be beneficial for other operators who have an experience gap in conducting similar operations.