Cost-Effective Fracturing Assessment Based on Wellhead High-Frequency Pressure Monitoring Technology

Multi-stage volume fracturing technology in horizontal wells play a significant part in large-scale recovery of domestic unconventional resources such as tight or shale oil and gas. High-efficient fracturing assessment is of great importance to multi-stage fracturing optimization. The traditional fracturing assessing technologies, including micro seismic and tilt meter, are still deployed and served as frequently-used means in domestic fields. In North America, distributed optical fiber, down-hole video camera and ultrasound imaging etc. have been widely applied in unconventional resources development, which feature with advantages of high resolution, real-time acquisition, near-wellbore precise fracture characterization. Compared with traditional techniques, the application of above mentioned new fracturing monitoring technology is still limited by poor economic viability, inefficient assessment and poor field adaptability. The cost-effective alternative solution to on-line or post-frac monitoring and assessing methodology is really required towards unconventional resources recovery. To address above issues, one low-cost solution was proposed and applied to the field by Research Institute of Petroleum Exploration and Development (RIPED), PetroChina in this article. Novel surface high-frequency pressure measuring device was instantly connected to wellheads with specifications of maximum sampling frequency of 4000 Hz, maximum pressure threshold of 140 MPa and continuous sampling period of 30 days. One integrated assessing workflow was put forward aiming to evaluate fracture and clusters dynamic parameters of all stages. An adaptive de-noising and filtering method is also proposed to more precisely conduct diagnosis and assessment of abnormal responses, cluster uniformity and diverting operation. One shale-oil well with 38-stage stimulation was selected for field validation of this cost-effective fracturing monitoring and diagnosis solution. Average standard deviation of liquid-absorbed volume among clusters of all stages decreased from 0.53 to 0.19 after temporary plugging and diversion were completed. Perforation clusters efficiency of this well was also investigated and average value reached 83% among all stages. It is indicated by wellhead high-frequency pressure measuring system that temporary plugging and diverting materials positively contributed to generating fracture networks in this well. The expenditure of this cost-effective solution is approximately one fourth of optical-fiber-based monitoring technology as estimated by operators.