Real-Time Monitoring of Acid Stimulation Using a Fiber-Optic DTS System

摘要

This paper discusses a unique system that combines a fiberopticrndistributed temperature system (DTS) to measure therndistributed temperature across the entire wellbore and arnmolecular telemetry transmission system that provides arnsingle-point determination of bottomhole pressure. Thernsystem has been used to perform real-time downholernmonitoring of multi-stage acid-stimulation treatmentsrnperformed on wells that contain multiple non-isolated payrnintervals. The fiber-optic for the DTS is contained inside arnlength of capillary tubing, which is placed concentricallyrninside a larger size capillary tubing. The created annulusrnbetween these two strings of capillary comprises the molecularrntransmission system for determining the bottomhole pressure.rnReal-time-distributed temperature data and single-pointrnbottomhole pressure data are provided on location. In the casernhistory presented, the temperature profile across the multiplernpay intervals yielded valuable information for identifyingrnwhich zones were “taking” the acid, allocating how much acidrnthese zones were taking (relative to one another), andrnidentifying the zones not taking acid. This allowed on-the-flyrnchanges to be made on-site in real-time regarding the make-uprnof the acid treatment, the pumping rates, and when and wherernto apply diversion processes.rnThis system enabled the operator to continuously monitorrnthe wellbore temperature across the interval that was beingrnstimulated as well as from a single-point bottomhole pressurernbelow the lowest perforation. In this case, the system wasrndeployed inside the work string used for the acid stimulation,rnbut the system can also be permanently deployed.rnThe nominal ratings for this monitoring system are 250°Crnand 10,000-psi. This allows the system to be applied in arnlarge number of wells, either onshore or offshore.rnFurthermore, there are no downhole electronics and nornmoving parts, making the system extremely well suited forrnharsh environments.