Predicting and Mitigating Erosion of Downhole Flow-Control Equipment in Water-Injector Completions

Abstract

Abstract Several large projects currently being developed will require high rates of water injection to sustain field life. Several operators are considering installing DownHole Flow Control (DHFC) equipment in these wells. The effects of erosion on this type of equipment could be catastrophic. Erosive effects must be accurately predicted in order to properly design equipment that mitigates them and ensures a long service life. To do so, BP and Baker Oil Tools performed a joint test program based on a likely injection program for fields in the Gulf of Mexico. The water injection program studied required an injection rate of 45,000 bbl per day in each well. The expected field life was set at 15 years, which meant that up to 250 million bbl of water could be injected into each well. The predicted solids content was around 1 lb per 1,000 bbl, or approximately 250,000 lb over the life of the well. This paper presents the study undertaken to predict and mitigate erosion effects under these injection conditions. Predictive studies using tools such as Computational Fluid Dynamics (CFD) software are discussed. These studies were used to change the physical geometry of the sleeves to minimize fluid velocities and erosive effects. Finally, a full-scale test of the newly designed equipment was conducted to determine the accuracy of the predictive model. The results also determined whether the configuration would minimize erosion to acceptable levels. The results of this testing are presented as well. Commentary on the predictive capability of software modeling and analysis of the test results is included. Opinions are given on the impact this study has on the future deployment of DHFC systems in these applications. Introduction The development of interventionless downhole flow control systems offers operators a method of maximizing production efficiency while minimizing operating costs. DHFC systems are ideal for subsea wells, where intervention costs can run into the tens of millions of dollars. The interventionless system jointly developed by BP and Baker Oil Tools provides two key elements critical to long-term success in water-injector wells. The first element is the ability to precisely control which zone, or portion of a zone, the water was being injected into. This helps the operator maximize sweep efficiency through the field. The second is the interventionless ability to switch between zones by remote actuation. Because the candidate wells are subsea, repeated intervention or workovers to perform this operation would not be cost effective. A schematic of the proposed completion is included (Figure 1). The initial completions will be for control between two zones. The system was designed to allow the flexibility of controlling up to six zones. Hydraulically controlled sliding sleeves with dedicated control lines were chosen as the isolation method for these zones.