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Collaborating Authors
Abstract Perforation erosion and consequential changes to perforation friction pressure have a significant practical influence on limited entry hydraulic fracturing treatments and have been comprehensively documented (Cramer 1987), (Crump, Conway 1988), Long (2015) and others. Both effects are widely acknowledged but undesirable phenomena that stimulation specialists encounter and must mitigate during every treatment. The emergence of the alternative fracture diagnostic method described in this paper means however that perforation erosion can also have beneficial consequences for those trying to diagnose and optimize fracturing performance. The latest generation of borehole video cameras efficiently capture high definition images of erosion to individual perforations after hydraulic fracture treatment. Qualitative and quantitative evaluation of these images allow confirmation of proppant placement and fracture initiation depths that are resolved to the location of individual perforations. The methods described updates the previous work of Roberts, Lilly and Tymons (2018) to now directly quantify perforation erosion. This improves the identification of clusters that have been successfully stimulated against those that are under or over-stimulated. Measurement and comparison of perforation erosion, area, diameter and azimuth permit a statistical evaluation of the consistency of fracture distribution across clusters and stages. In their goal for optimal recovery Stimulation Engineers, Geoscientists and Reservoir Engineers evaluating treatment success have a fundamental question to answer - where exactly did the frac go? This apparently simple question has hitherto proven difficult, and costly, to answer. We demonstrate that evaluating perforation erosion provides straightforward and intuitive data to precisely confirm proppant placement, define the origin of individual fractures and help quantify treatment distribution. We present results illustrating the effectiveness of the method including examples of acquired perforation images. New methods are introduced demonstrating evaluation techniques used to confirm proppant transport through specific perforations, fracture initiation and treatment consistency. Initial work to demonstrate in-situ correlation between erosion and pumped proppant volume / weight is presented. We conclude that the method can be successfully applied to evaluate changes to stimulation treatment design parameters such as stage length, cluster number and spacing, proppant and fluid properties, pumping criteria and many aspects of perforation design including perforation charge type, count per stage and cluster and shot orientation. Existing hydraulic fracture diagnostic methods are limited in number, scope and sometimes accuracy. Analysis of in-situ perforation erosion using visual analytics provides an additional and complementary data source to evaluate the success of engineered treatment programs. The method provides measurements at a depth resolution that is not otherwise possible, allowing specific entry holes and fracture initiation points to now be evaluated.
- Research Report (0.68)
- Overview (0.48)
- Geophysics > Seismic Surveying > Borehole Seismic Surveying (0.34)
- Geophysics > Borehole Geophysics (0.34)
Abstract Improving cluster efficiency is critical for economic and efficient multi-cluster per stage fracturing in unconventional shale & tight horizontal well completion. This paper highlights the findings from a field trial to test different perforation design variables which contribute to cluster efficiency. The goal was to optimize perforation design parameters and improve cluster efficiency for a given stage, and thus the well in its entirety. A two well trial was conducted across the same bench formation on a single pad in Midland Basin. In all, eight perforation designs were created using two set points (high and low) across three key perforation design variables: 1) perforation phasing & orientation, 2) perforation diameter, and 3) perforation friction. Each design was repeated eight times (i.e. eight stages) to allow for a meaningful number of data points. After stimulation operations were conducted an acoustic imaging technology was utilized to assess the perforation dimensions for all perforations post-fracture for all stages as well as various sets of pre-fracture perforations. In total, the trial was conducted across 64 stages (8 perforation designs × 8 stages per perforation design) using a Design of Experiments (DoE) method to assign low or high set points for each perforation design to best ascertain the impact of each test variable on the response variable as well as test for multicollinearity across the test variables. The uniformity index metric was used as a proxy for cluster efficiency and was calculated using two methods (a) eroded perforation area increase, and (b) post frac perforation area. Based upon the results obtained from the acoustic imaging data set and the subsequent data analysis, the uniformity index improved with a perforation design that had higher average perforation friction, smaller perforation hole shot size and a 0 degree in-line perforation orientation. The field trial results of uniformity index provided high quality statistical quantification of optimum perforation design parameters and its impact on cluster efficiency.
- Research Report > New Finding (0.68)
- Research Report > Experimental Study (0.54)
- Geophysics > Borehole Geophysics (0.69)
- Geophysics > Seismic Surveying > Borehole Seismic Surveying (0.55)
- North America > United States > Texas > Permian Basin > Midland Basin (0.99)
- North America > United States > Texas > Permian Basin > Delaware Basin (0.99)
- North America > United States > South Dakota > Williston Basin > Bakken Shale Formation (0.99)
- (4 more...)
Abstract Recent step changes in downhole video technology and image analysis have coincided with a growing understanding of how perforation erosion can be used to measure the effectiveness of limited entry hydraulic fracturing. This has led to rapid growth in video-based perforation imaging and produced a substantial database of measured and statistically analysed perforations. A review of recurring patterns and common trends identified in the database provides useful insights on proppant placement and distribution. An analysis was undertaken on a dataset that includes detailed individual perforation dimensions from more than 6,000 clusters and 600 stages. With a focus on understanding the uniformity of proppant distribution, the initial phase was to identify significant recurring patterns in cluster level proppant placement derived from perforation erosion measurements. Multiple treatment design parameters were then analysed to understand their influence on proppant distribution. Among those considered were stage length, number and spacing of clusters per stage, the number of perforations shot per cluster, perforation charge type and phasing. While every well produces a unique set of results, several recurring trends were identified across the database. These often indicated sub-optimal proppant placement with undesirable consequences for production and ultimate recovery. Results demonstrate thatProppant placement is often significantly non-uniform across a stage A strong tendency for greater heel-side perforation erosion is typically observed for ‘geometric’ stage and cluster designs A similar strong preference for proppant to be placed in perforations located towards the low-side of the wellbore is also apparent More uniform proppant distribution can be obtained using an engineered design approach Although they are often inter-related several treatment parameters can be engineered with relative ease to produce more uniform proppant placement Analysis methods, results, treatment parameter considerations, primary conclusions and other relevant findings will be discussed in detail. The majority of research on treatment design parameters that influence proppant placement has mainly used CFD-DEM models. The approach presented in this paper, however has used empirical, in-situ data. The size of the dataset and the frequency at which certain tendencies are observed provide some confidence that the approach and results are valid and can help improve treatment design. It is hoped that the results of the study will provide hydraulic fracture specialists with further evidence-based guidelines that ultimately help increase production and enhance ultimate recovery.
Abstract This paper further develops an analysis of proppant distribution patterns in hydraulically fractured wells initially presented in SPE-199693-MS. A significantly enlarged database of in-situ perforation erosion measurements provides a more rigorous statistical basis allowing some previously reported trends to be updated, but the main objective of the paper is to present additional insights identified since the original paper was published. Measurements of the eroded area of individual perforations derived from downhole camera images again provide the input for this study. Entry hole enlargement during limited entry hydraulic fracturing provides strong and direct evidence that proppant was successfully placed into individual perforations. This provides a straightforward evaluation of cluster efficiency. Perhaps more importantly the volume of proppant placed into a perforation can also be inferred from the degree of erosion. Summing individual perforation erosion at cluster level allows patterns and biases to be identified and an understanding of proppant distribution across stages has been developed. Outcomes from an analysis of a database that now exceeds 50,000 eroded perforations are presented. Uniform reservoir stimulation is a key objective of fracture treatments but remains challenging to measure and report. The study therefore focused on understanding how uniformly proppant is distributed across more than 1,800 measured stages. Results demonstrate how proppant distribution within stages is influenced when treatment parameters change. Our approach was to vary one parameter, for example the stage length, while all other parameters were maintained at a consistent value. We investigated multiple parameters that can be readily controlled during treatment design and show how these can be manipulated to improve proppant distribution. These included stage length, cluster spacing, perforation count per cluster and perforation phase. Hydraulic fracturing is a complex, high energy process with numerous input parameters. At individual cluster and stage level outcomes can be unpredictable and diagnostic results are often quite variable. The approach taken here was to complete a statistical analysis of a sufficiently large dataset of in-situ measurements. This allowed common trends and patterns to be confidently identified and conclusions reached on how proppant distribution is affected by varying specific design parameters. This should be of interest and value to those designing hydraulic fracture treatments.
- Research Report > New Finding (1.00)
- Research Report > Experimental Study (1.00)
Abstract Plug failures, sub-optimal stage design and variable proppant distribution across multi-cluster stages are common issues experienced during plug and perforate hydraulic fracturing. When one or more of these problems occur production potential can be significantly reduced. This case study shows how an operator in the US succesfully applied state-of-the-art fracture diagnostic methods to identify, understand and address these problems and demonstrated improved performances for all three issues in the subsequent wells. Selecting the right stage design is a crucial factor in the success of a fracturing operation. With three different designs being considered for use during a new development the operator used perforation erosion measurements on the initial well to evaluate how uniformly proppant was placed within each stage. Data was acquired using a new diagnostic service combining array Ultrasound and array Video sensors. Previously considered as competing services, with users required to select one or the other, combining both technologies and simultaneously acquiring the data provided some clear benefits and improved understanding which are discussed in detail. The combined technologies provided more comprehensive diagnostics than either sensor could deliver alone. Potential issues with missing data – due either to proppant-filled (plugged) perforations or poor optical clarity - were mitigated resulting in never before achieved levels of data completeness for both surveyed wells. This significantly improved statistical accuracy and provided unequivocal results. In the first well one of the three stage design options was clearly identified as providing better proppant distribution, with 27% higher uniformity than the second-best design. However significant low side perforation erosion was measured for all three designs and casing breaches were observed at some plug setting depths. This indicated the potential for further improvement on future wells, and a change in perforating charge type was recommended along with a review of the plug design and setting procedures. With these changes applied on the subsequent well, the expected improvements were duly delivered. This evolution of stage design was confirmed as providing the best result overall, and with a substantial improvement in uniformity than had been previously achieved in well 1. In conjunction, the revised plug setting procedures eliminated the issues at plug setting depths that had previously been witnessed. The paper aims to provide anyone targeting improved well performance by using fracture diagnostics with up-to-date knowledge of perforation imaging methods. This will allow informed decisions to be made on how to best deploy the technologies. The case study demonstrates how these methods can be readily applied to identify and resolve common fracture treatment issues, with defining optimal stage design of particularly high value. Learnings can then be used field wide to improve proppant uniformity and ultimately production.
- North America > United States > West Virginia > Appalachian Basin > Marcellus Shale Formation (0.94)
- North America > United States > Virginia > Appalachian Basin > Marcellus Shale Formation (0.94)
- North America > United States > Pennsylvania > Appalachian Basin > Marcellus Shale Formation (0.94)
- (3 more...)