Holistic Approach of Acid Stimulation Selection in Carbonate Fields for Productivity Enhancement

Abstract

Abstract Carbonate rocks constitute a significant portion of hydrocarbon reservoirs worldwide. Due to their unique geological deposition, carbonate formations have different ranges of heterogeneities such as mineralogies, permeabilities, fluid properties, fissures, natural fractures, and reservoir pressures. On top of their inherent heterogeneities, well operation activities such as drilling and well intervention can damage the formation. In the lower-permeability formations, a maximum reservoir contact (MRC) well is a preferred option to extract hydrocarbon from the reservoir. An MRC well involves specific challenges from the well completion perspective that eventually could impact the productivity. Carbonate stimulation is a long-standing technique to increase productivity in carbonate formations. Stimulation treatment in general improves the hydrocarbon deliverability to the wellbore and eventually to surface. It also removes or, on some occasions, bypasses the damage in the wellbore. With a long horizontal well, more surface area must be stimulated; however, more surface area means there is more heterogeneity to overcome as well. This paper describes the importance of acid stimulation planning as well as modeling, which plays a vital role in effectiveness of acid stimulation job in horizontal wells with different MRC completion types and achieving the best results of productivity enhancement in carbonate fields. Log-and-completion-based simulation software was used to model the formation heterogeneity in combination with well completion complexity. Different modeling scenarios based on well trajectory and completion design are simulated together with the reservoir heterogeneity such as different permeability, possible fissures, different reservoir pressures. Different acid systems are also simulated against these heterogeneities and complexities. The stimulation modeling results show that stimulation uncertainties arise when both completion complexity and reservoir heterogeneity are present. A stimulation integrated workflow following the stimulation design workflow in the latest log-and-completion-based software is presented. Some case studies in UAE related to these challenges are presented with some key lessons learned. Some advanced carbonate acidizing technologies are implied in this observation to achieve the stimulation objectives.