Prediction and management of solids production in typical Surat Basin coal seam gas reservoirs, eastern Australia

Abstract

The exploiting of coal seam gas (CSG) reservoirs worldwide has developed rapidly. These reservoirs are located in different geological settings and have different characteristics. In eastern Australia for instance, Surat Basin CSG reservoirs are typically thin and interbedded with thick layers of sandstone, siltstones and shales, and occur at shallow depths, adjacent to fresh-water aquifers. For commercial gas production from wet- and low- permeability thin CSG reservoirs, both the hydrostatic pressure and the water saturation have to be reduced through a de-watering and pressure depletion process. These mechanisms increase the risk of rock failure and solids production before or from the onset of gas production in many CSG wells. In thinly bedded CSG reservoirs, solids production from coals may not be a concern, but sanding from interbed rocks—some with abundant water sensitive clay minerals—may be a significant source of solids production. Given the relatively low drilling and completion costs and short life span of the CSG wells, many of the conventional sand control measures such as screens or gravel packs may be of limited use or not applicable. In this extended abstract, examples of solids production issues and the potential sources of solids in typical Surat Basin CSG wells are shown, and options for solids control are discussed.