A concept platform integrating the precise movement of a linear or azimuthal actuator, such as in instrumented wireline intervention tools (IWIT), with fast pressure measurements or rock/fluid sampling instruments is presented. This device accurately moves the measurement probe or sampling assembly either in the longitudinal or azimuthal direction in the wellbore to significantly improve operational efficiency and data quality.
Precise down-hole movement control enables the collection of pressure data or rock/fluid samples at exact depth increments hence eliminating errors induced by cable stretching, overpull, or variable cable creep. Specific lithofacies could be targeted from a borehole image log combined in the platform. Simulation with current IWIT capabilities shows significantly reduced uncertainty over common wireline protocols. The operational procedure includes correlation using standard wireline gamma ray methods, then the platform is anchored at the top of the interval of interest and the linear actuator is used for probe displacements. Inchworm movements can also be performed to extend the length of the probe displacements. Removing cable movement for probe displacements significantly reduces the biggest source of error in distributed pressure measurements. Similar approach is proposed for the coring tool with the added benefit of being able to rotate the drilling bit at different azimuths to collect rock samples.
This concept platform would reduce the time spent on pressure surveys if similar accuracy to current practices is acceptable. Because the biggest remaining source of error is gauge accuracy, simulation results show that fewer stations are needed to replicate standard wireline results. Where accuracy is important, as with pressure measurements to quantify reserves using gradient intersection to define fluid contacts or validate compositional fluid gradients, the proposed approach is shown to significantly reduce error using equal number of stations. We use data sets from previous work to show the impact of the error reduction in the position of fluid contacts.
IWITs currently used in cased hole employ active anchoring to perform intervention tasks. Applications of linear actuators in cased hole operations today include pulling and pushing movements to manipulate completion components. The controlled downhole force available for these operations goes up to 80,000 lbf while the anchoring force could be up to 150,000 lbf. In the proposed concept platform, this pulling force could be instrumental in cases with elevated risk of differential sticking. By anchoring the upper part of the platform in overlying impermeable intervals, only the pressure probe or rock/fluid sampling assembly is lowered into the permeable interval to conduct the operation without exposing the full length of the string to the pressure differential forces and hence mitigating the risk of sticking.
The proposed architecture for the concept platform combines several operational elements used today as separate entities in wireline operations. Their integration, however, generates important efficiency gains, reduces risk in pressure measurements and fluid sampling and sidewall coring operations, improves accuracy, and enables the implementation of unprecedented distributed pressure measurements and coring practices with azimuthal positioning capabilities using wireline.
