Abstract
The fracturing designs used in the development of Jafurah unconventional field have evolved over time incorporating local experience and innovations as well as best practices implemented in other basins. One of the latest productivity trials included the use of High Intensity Fracturing (HIF), where the number of generated fracs per stage are significantly increased by decreasing the cluster spacing, increasing the number of clusters and increasing the proppant volume per stage and at the same time using the engineered limited entry (ELE) as the technique to enhance cluster efficiency.
The trial was designed in a systematic approach to minimize the impact in operational efficiency and well stages delivery. It included different operational phases to prove the design concept, and to ensure fracture placement until a full pad trial execution was conducted. The first phase involved perforation limited entry design de-risking and implementation; second phase included the successful execution of HIF design jobs in several stages; and finally, two complete wells in a 4-well pad were stimulated with HIF design to compare its placement and productivity with the other 2 wells in the pad stimulated with a standard design. As part of the surveillance, fiber optics cross-well monitoring was performed to characterize the fracture growth and resulted SRV from the different stimulation jobs.
Step-down test analysis was used to compare ELE designs vs the standard perforation scheme used in the field. Results showed that high friction perforation design enables higher cluster efficiency during the frac jobs, resulting in close to 100% efficiency. HIF design with different perforation schemes 2-holes/cluster and 3-holes/cluster along with volume optimization were trialed in the second phase and it was decided to move forward with a 3-holes/cluster design due to higher pressure response and well head pressure restrictions. Finally, 2 complete laterals were successfully completed with the HIF design resulted from the operational trials. Stages were placed with 100 % success rate while some standard stages were challenging to place. Fiber optics monitoring using strain analysis allowed a characterization of the frac designs giving insights on the stimulated reservoir volumes by evaluating, volumes and times of first response, fracture intensity and magnitude. Fiber data showed that frac corridors generated with standard design reactivated significantly high fracture network from previous stages and low frac generation in virgin rock. On the contrary, high intensity fracturing design exhibits a more effective fracture corridor in new rock with less interference with previous stages. Production response for the different frac designs were assessed.
High intensity fracturing and engineered limited entry resulted in a robust design, with no proppant placement issues, that generated a higher intense fracture network than the standard design.
