Impact of Completion and Stimulation Techniques on Water Injection Flow Conformance in Carbonate Reservoirs

Abstract

Abstract Drilling of long lateral sections enables operators to execute development schemes that require fewer wells with a lower overall carbon footprint. Water injection wells help sustain reservoir pressure and provide sweep to maximize field commercial recovery. A key challenge is to divert the water along the drain length to achieve uniform injection profile. In this paper, we compare different completion and stimulation techniques with special emphasis on wellbore accessibility and injection conformance along the lateral. We first group the wells according to the completion type, which can be either open-hole or cased hole. Cased hole completions are then subdivided into slotted liners, Smart Liners, and completions with zonal control. The type of completion dictates the options available for acid stimulation, which can involve either high-rate bull-heading, coiled-tubing deployed techniques or no stimulation. The analysis of conformance involves injection logging tool results as well as the reported percentage of the wellbore accessible for intervention tools. Most of the existing well stock consists of wells completed open-hole with limited or no stimulation. Abrasive jetting can provide effective stimulation but often deliver a skewed injectivity profile. Bull-heading of acid from surface, on the other hand, is not usually applied in water injectors due to higher stimulation equipment and chemical costs. Furthermore, undulating trajectories can substantially reduce the wellbore accessibility in open-hole completions. Installing a liner improves accessibility significantly. Our analysis of injectivity profile logs shows that a lower completion with zonal compartmentalization provides a more uniform injection profile compared to a barefoot completion. A uniform injection profile is achieved by either ICD (with associated SSD) or Smart Liner Completion. Injectivity data suggest that the pre-and post-stimulation injectivity index is comparable between ICD and Smart Liner Completions, which is not surprising since both techniques rely on the limited-entry principle for fluid diversion. This paper offers a comprehensive comparison of completion-stimulation techniques for carbonate reservoirs and offers some guidelines for selecting a suitable method depending on the well and reservoir characteristics, such as well length, permeability, permeability variation, and anticipated need for future interventions. We also provide results from a simple 2D finely gridded numerical simulation model using a producer-injector pair to illustrate the impact of high permeability streak on early time water breakthrough. Results indicate that blocking the high-streak either at the producer or at the injector leads to similar water-cut evolution. Blocking the interval in both wells from day one is better and blocking a 50ft interval on both sides of the streak is even better.