Achieving Target Solids-Free Gas Rate from Highly Unconsolidated Sandstone Formation Intervals

摘要

One of the most challenging aspects of producing wells drilled in the northernmost section of the unconsolidated pre-Khuff gas bearing reservoirs in Saudi Arabia is to achieve solids-free production while trying to achieve high gas rate targets. A high degree of success in meeting this challenge has been achieved by implementing a fracturing for sand control strategy, whereby proppant fracturing treatments with a tip screenout design and a combination of other techniques have been successfully placed in a number of producers throughout the gas development program. Subsequently, challenging reservoir conditions, including high temperature and pressure, high stress, heterogeneity, and the absence of stress barriers make placing the fracture treatments very difficult, time consuming and expensive. Therefore, in pursuit of optimum, simple, and cost-effective solutions to the challenge of achieving solids-free gas production, Saudi Aramco successfully set stand-alone screens in wells completed open hole in a sandstone reservoir, and achieved excellent results while significantly reducing costs by eliminating the need for a fracturing treatment and streamlining all other operations. This paper provides details about the geology of the sandstone reservoir, well and screens selection criteria, the screens deployment procedure, post-deployment results, and lessons learned from a two well pilot test. The successful results achieved from the pilot test opened the door for further implementation of the technology and optimization steps. Introduction Achieving solids-free production from unconsolidated sandstone reservoirs is an ongoing challenge. The importance of achieving effective sand control in wells drilled in this type of reservoir derives from the need to maintain the integrity of bottom-hole and surface processing equipment and facilities, and ensure production targets are met on a consistent way. Examples of the potential damage caused by sand production are shown in Fig. 1. The heterogeneous nature of the gas producting sandstone reservoirs, with widely varying porosity and permeability, has prompted a search for engineering solutions to try to optimize and maximize well productivity from both relatively high and low permeability intervals. A number of different approaches, including indirect hydraulic fracturing stimulation, high angle and increased contact wells, and more recently, sand screened completions have been adopted by Saudi Aramco to develop vast gas reserves. Among these approaches, sand screened completions, on both vertical and high angle wells, was initially field tested in two wells, and expanded to more after the success of the pilot.