We demonstrate how numerical analysis of downhole video images can be used as an effective decision enabling tool to improve the efficiency and cost-effectiveness of acid or proppant based hydraulic fracturing treatments. We illustrate how in-situ downhole video-based perforation measurements provide direct and quantifiable visual evaluation of perforation entry hole geometries, and how this information enables well operators to improve fracture distribution, optimise treatment pressures and rates and reduce the risk of screen-out.
Video images provide a unique method of acquiring previously unavailable downhole perforation dimensions that are a key input to successful hydraulic fracture design. Along with this new source of data we introduce the concept of video analytics, and describe how customised digital image processing methods have been developed to quantify perforation dimensions. We describe new analysis methods that provide insight into the in-situ distribution of perforation dimensions.
This paper illustrates how the application of a complete system comprising downhole instruments, operational procedures, automated digital image processing methods and data analysis techniques is used to measure, understand and report the dimensions of perforations. We describe how in-situ high definition video images of perforations suitable for numerical analysis during stimulation operations are obtained. We also describe how a downhole image calibration method along with new video analytics tools comprising customised digital image processing software and bespoke statistical analysis techniques is used to derive detailed understanding of perforation geometries and deliver a concise report of their dimensions. We discuss the relationship between measured results and stimulation treatments, and how these can be optimised to ultimately improve well productivity and long-term recovery.
Wellbore back pressure, or ‘perforation friction’, plays a critical role in the even distribution of fractures during limited entry hydraulic fracturing operations. Perforation size is a controlling factor in calculations used to determine the optimal perforation friction necessary for even fluid distribution during treatments, but is currently derived indirectly and incompletely from surface measurements. Crump and Conway (1988) demonstrated that erosion of perforation entry hole diameter has a significant influence on perforation friction values during treatment. It is shown that, compared with surface derived values, in-situ downhole measurements of perforation entry hole area and geometry increases calculation accuracy. We conclude that directly measuring this key parameter downhole leads to improved control of the fracturing process and efficiency gains with respect to pumping capacity and treatment volumes. Results also demonstrate that fracture distribution can be improved using in-situ measurements of perforation entry hole geometry.
We show that downhole perforated hole dimensions, when analyzed by stage, cluster or at the individual level, can be used to refine perforation strategies and treatment pressures/rates. The method also provides valuable input to calibrate other monitoring techniques. We also conclude that valuable qualitive visual information on perforation and wellbore conditions in both pre- and post-fracturing operations are often recorded alongside quantitative measurements.