Use of Real-Time BHA Data to Enhance Predictability and Safety of Coiled Tubing Solids Removal Operations in New Zealand

Abstract

Abstract Coiled tubing (CT) cleanout operations in New Zealand require extremely detailed planning and execution. When significant proppant is left in the well as a result of hydraulic fracture screenout, customer concern requires ensuring that hydrocarbons are not produced and returned to temporary surface equipment during the cleanout operation. During solids removal, the solid rate of return at surface must be limited to prevent erosion of flowback equipment. To reduce operator uncertainty during this process, modeling with a solids transport simulator, along with a real-time downhole communication system, was used to provide real-time pressure data at downhole conditions. To provide an engineered cleanout, one of the modeling goals was to determine the predicted maximum solids return rates so the flowback choke integrity was maintained. Real-time monitoring of downhole information during the operation enabled a hydrostatic pressure calculation based on true vertical depth (TVD) to determine the equivalent circulation density (ECD) of the fluid column. Determining the ECD enabled the estimation of the solids concentration in the fluid returned via the annulus (tubing/CT). Consequently, an increase of hydrostatic pressure (relative to water) at downhole conditions correlated to an increase of solids concentration in the fluid column during the cleanout phase. By monitoring this increase in the ECD during the sand cleanout, the operator had an early indication of an increase in solids concentration in the fluid returns. This knowledge enabled the operator to manage the flowback operation at the surface, without exceeding surface equipment specifications. The process met customer requirements for enhanced proppant cleanout operations. This paper details the background of the operator cleanout requirements, the pre-job design analysis used, the job parameters during execution, and the incorporated improvements made compared with conventional well interventions.