Four Steps to Successfully Stimulate Thin Layers in a Laminated Reservoir

Abstract

Abstract Hydraulic fracturing is well known as an economics enabler for tight reservoir development by accelerating gas recovery. However, tight reservoirs are often associated with low permeability, high Young's modulus layers, thin laminated sands, and influence from tectonic forces. These factors increase the challenges in proppant placement and require a specialized strategy and approach to enable placement and create an economically favorable well. A novel approach that consists of four steps was introduced to eliminate observed proppant placement challenges in a tight gas reservoir in Oman. Ensuring the wellbore-to-reservoir connectivity with deep-penetrating perforation methods is the first step to establish the connectivity in formations with high unconfined compressive strength. The second step is to avoid poroelastic effects in the thin reservoir by minimizing total injected fluid and modifying the sequence of diagnostic injection steps. This is followed by a modified hybrid treatment to minimize the excessive net-pressure development due to viscosity-dominated reservoir behavior. The final step is a pulsing pumping methodology with fiber to better enable placement through narrow fracture widths. These four steps were implemented successfully and enabled the full placement of stages in several wells in which proppant placement had previously been a challenge. A further analysis aimed to rank the level of impact of each step on proppant placement. Avoidance of poroelasticity, minimizing the viscosity-dominated impact, and having the ability to pump the proppant through a narrow fracture width using a pulse methodology are the main contributors to the success. Indeed, the quality of the fracture placed is directly proportional to incremental gas production from each zone. The assessment process to address the challenges observed in tight reservoir development and the evidence to support this strategy are documented. Optimization of each method continues by applying lessons learned and tracking the outcome of each step of the treatment. An integrated surveillance strategy also provides longer-term understanding of the production successes from each treatment.