Breaker Placement in Sand Control Lower Completions – New Challenges and Potential Solutions

Abstract

Production and injection wells for oil and gas and carbon storage reservoirs often require sand control across the reservoir section to enable fluids to flow and to prevent larger formation solids from moving. In many of these wells, chemical breaker treatments are pumped prior to production or injection to help to reduce any drilling or completion induced formation or completion damage. Delivering these breakers to the target such as residual drilling mud cake can be challenging and rules of thumb have often been used to guide this process. More rigorous methods to optimise breaker placement and design are now available. CFD (Computational Fluid Dynamics) enables fluid flow in complex geometries to be modelled and predicted. Breaker placement during the well completion process involves the complex geometry of the well, the lower completion and the reservoir and fluid flow or displacement. The full geometry of vertical or horizontal wells, with induced fractures, multiple wellbores, perforations or mini-bores should and can be captured using CFD. Breaker pumping whether bull-headed, through a wash pipe, coiled tubing or more sophisticated rotating and jetting needs to be simulated in order to determine its efficiency. Numerous simulations for different well types, completions and breaker deployment methods have revealed that even with the best intentions and rules of thumb, it can be challenging to place breaker to the target and for breaker concentrations required for efficient dissolution of residual damage to be maintained. In particular gravel packed completions present challenges. Fluids will always take the path of least resistance and in gravel packed completions this is often back up the well between the wash pipe and the screens missing the intended target. The additional resistance of the gravel in the annulus tends to prevent efficient breaker penetration to mud cake or perforations beyond. If the breaker does penetrate, then coverage of the damaged zone can be patchy and early losses can result. Simulations have also identified potential mitigations such as alternative deployment rates, displacement fluids prior to breakers and duration of breaker placement. The benefits of targeted breaker placement during pump and pull or jetting operations has also been evaluated. Challenges in placing breaker effectively in sand controlled wells are addressed using complex numerical modelling. Replicating well geometry and all fluid flow paths are essential in order to optimise breaker placement and reduce residual formation and completion damage. The methods and examples shared will enable more effective clean-up of oil, gas, water, hydrogen and CO2 wells.