Print this pageLocal and Regional Almond Formation Reservoir Connectivity Determined from Produced Water Chemistry, Washakie Basin, Wyoming
SMITH, LETA K., and RONALD C. SURDAM
Sweetspot wells in the Almond Formation at Standard Draw-Echo Springs field produce more gas than can be accounted for by volumetrics of completed zones alone. However, since the produced water exhibits a range of compositions reflecting the original depositional environment, its chemistry was used to determine the source of the produced water and therefore of the produced gas. The sweetspot wells produce fresher, more bicarbonate-rich water from the Lower Almond even though they are completed in the Upper Almond marine facies. Further, geochemical modeling of the water suggests that fractures, which are present throughout the field, are least cemented in the sweetspot because fracture-filling cements, particularly calcite, are unstable in there. Therefore, in the sweetspot, water and gas from the Lower Almond are allowed to produce through Upper Almond perforations. A second fracture network connecting the Almond with deeper zones is also demonstrated by the produced water. Throughout the basin, Almond water with anomalously high total dissolved solids (TDS) is produced from wells adjacent to major surface-mapped lineaments. For example, where one of these lineaments intersects Standard Draw-Echo Springs field, the produced water has a higher TDS, and chemical geothermometry of the water indicates a deeper, hotter source. Thus Almond Formation produced water chemistry can be used to assess fluid flow compartmentalization and connectivity at a range of scales.