Cemented Single Point Entry (CSPE) has the potential to reduce or eliminate the non-uniformity and Hydraulic Frac Stimulation (HFS) placement uncertainties inherent in other completion systems. If entry-to-entry isolation can be achieved, HFS initiation and treatment allocation near the wellbore can be better controlled by a CSPE completion. Fiber Optics (FO) and other diagnostics can provide the means to evaluate the effectiveness and potential benefits of this and other completion systems. This paper describes the HFS placement findings of a FO instrumented Coil Tubing activated CSPE well (CTa-CSPE).
Coil Tubing CSPE completions provide some additional frac diagnostic information. Pressure and Temperature (P/T) gauges located in the Coil Tubing Bottom Hole Assembly (CT-BHA) help to evaluate the isolation with prior stimulated stages. A newly developed sleeve, specially designed to accommodate a FO cable outside casing, allows the simultaneous acquisition of both P/T information from downhole gauges and high-resolution stimulation data from FO.
This paper shows several examples from stages with variable entry-to-entry isolation quality in a wellbore with 6000 ft lateral section. The results from the P/T gauges, Distributed Acoustic Sensing (DAS) and Distributed Temperature Sensing (DTS) are mostly consistent for all 69 stages in this well. Only stages where communication was observed toward the heel-side of the lateral, relative to treatment sleeve, show inconsistent but explainable results. CT-BHA P/T gauges are only capable of detecting communication toward the toe-side of the lateral. In this well some degree of communication occurred in 48% of all stages. Evaluation of the FO data across multiple stages shows that the path of communication between sleeves and slurry placement can be complicated. Integration of DAS and DTS indicates that the slurry, between adjacent and poorly isolated stages, travels behind the casing down to the prior sleeve and then inside the wellbore, where the slurry is partially re-injected into previously stimulated stages. This dataset clearly illustrates that no single HFS diagnostic provides all the necessary information to fully understand the complexities of HFS placement. In this well, the data from CT-BHA P/T gauges, DAS and DTS are clearly complementary. The data also indicate that there is an urgent need to improve isolation between stages. Cement quality seems to be the primary source of entry-to-entry communication in long horizontal wells for this and other completion systems. In this well alone we estimate several hundred thousand US$ were wasted from the misplacement of stimulation energy and materials (capital inefficiency). To capture the full value from CSPE "pinpoint-fracturing" and the corresponding more effective drainage of resource volumes between wells, the problems associated with entry-to-entry communication must be understood and corrected.
Finally, we will introduce some new multicycle sleeves that will further enhance the capabilities of CSPE systems. These sleeves are specially designed to obtain production profiling information via FO. Deployment of such systems should provide the industry with the means to better evaluate and optimize completions and wellbore spacing.