The SPE Hydraulic Fracturing Technology Conference (HFTC) was last week. There were tons of great, practically relevant, papers. People are really locked-in on the key value drivers. This blog post gives a sampling of a few of the papers that I found most interesting. I don’t discuss any of the ResFrac papers because they were in a previous blog post.
The “Observation Lateral” project from Hess (Cipolla et al., 2022) is an important new dataset. They drilled a long-term pressure observation lateral alongside producing Bakken/Three Forks wells. The well allows them to directly measure pressure changes during production and validate that they are getting depletion in the Three Forks from their Middle Bakken wells at 450 ft lateral offset. This is a hot topic because Bakken operators typically winerack their wells between the Middle Bakken and the Three Forks benches. The relative communication between MB and TF is important to understand because it impacts well spacing. Fractures definitely grow down from MB to TF, but the Lower Bakken (between the layers) is a clay rich layer that is suspected to squeeze shut on proppant and potentially act like a baffle between the zones.
Cipolla et al. (2022) show unambiguously that yes, they are getting production in the Three Forks from the Middle Bakken wells, even though the wells are placed in an area with ‘relatively thick’ Lower Bakken layer. There are a host of other details from the project, which included a full suite of diagnostics, such as offset fiber, sealed-wellbore pressure monitoring, and microseismic, and there are several other papers at HFTC about this project.
In ResFrac, we have been working with Hess on their Observation Lateral dataset as part of the Parent/Child Industry study. The pressure observations give extraordinary calibration data for parameters like fracture conductivity during both fracture propagation and long-term production. Hopefully, we’ll be able to share those results down the road.
Hess tested three different completion designs along their laterals, and compared them on the basis of pressure drawdown in the observation well and flow allocations from tracers. The diagnostics were consistent in assessing that one of the three designs had to better production than the other two. Unfortunately, Hess isn’t making public what the three designs were!
Ballinger et al. (2022) also addressed the topic of MB/TF communication. Interestingly, based on interference tests, they concluded that their MB and TF wells (spaced at 600 ft) did not maintain communication past 3 months. Why the different results from the Cipolla et al. (2022) study? A few possibilities: (a) there is a difference between 450 and 600 ft spacing, (b) they used different completion designs, or (c) there could be differences in geology between the areas.
I am personally interested in doing more work to understand the sensitivity of interference tests. Is it possible that interference tests could give false negatives – suggest a lack of communication, where some actually exists? This may depend on factors like the fluid compressibility and duration of the test. Keep an eye out – maybe we’ll address this topic in a future paper.
HFTS2 is a very important field-scale project that was performed in the Delaware Basin by a group of operators. The first batch of papers on the project was written at URTeC last year. There are more HFTS2 papers at HFTC, and I would particularly flag the Huckabee et al. (2022) paper as being worth a read. They have very interesting results documenting the effectiveness of limited-entry completion, and the limits, at different stage lengths and designs.
Also, if you’re interested in limited-entry, Barhaug et al. (2022) and Ribeiro and Zurovec (2022) both provide case studies documenting great effectiveness from limited-entry designs. However, watch out! Watson et al. (2022) continues a string of papers from ConocoPhillips on the practical risks to successful limited-entry designs. They continue to document major risks from plugs that fail (thus causing communication back to the previous stages), uneven hole size, and flow channeling in the annulus outside casing. They show that if you work to diagnose and mitigate these issues, they are (mostly) solvable. But if not, they could have major impact on production, and you may not even realize.
Next up, there were several papers on the topic of proppant dynamics in the wellbore. There is a theory that proppant may have difficulty ‘turning the corner’ to enter the heel-side perforations where velocity is highest. Eckdahl et al. (2022) provide an excellent case study using downhole imaging and fiber. Especially, they have a really good literature review. For anyone interested in learning more, I’d recommend starting with this paper.
Snider et al. (2022) was a standout because they addressed the ‘proppant dynamics’ topic with a direct physical experiment. This is critical, and uncommon, because most papers on the topic of have used computational fluid dynamics (which may be affected by modeling assumptions) or field-scale data (which are affected by the limited-data and complexity of practical field-scale data collection). By running controlled, full-scale, surface experiments, Snider et al. (2022) are giving us high-fidelity results that we can rely on. Largely, they agreed with prior papers that yes, proppant really does have a hard time ‘turning the corner’ at the heel-most perforations. But – here’s a really interesting and notable finding – this was only true for the 40/70 proppant. The 100 mesh proppant was placed almost uniformly.
In ResFrac, we have a simple correlation that causes proppant to struggle to ‘turn the corner’ as a function of fluid velocity. However, with some of these new results coming out, I intend to revisit that correlation and make it a bit more detailed and realistic.
There were tons of papers on sealed-wellbore pressure monitoring, and there were two in particular that stood out to me. First, Elliott et al. (2022) did some really quality engineering work linking laboratory experiments of casing deformation, computational modeling, and field observations. The study fills-in the technical details of what happens during a frac hit, and why sealed-wellbore pressure monitoring works. Second, Haustveit et al. (2022) did some very interesting work to map stress shadow as a function of distance from hydraulic fractures. One figure that stuck with me – they showed an excellent correspondence between the observations and the classic “Sneddon” equation predictions for stress shadow around a propagating crack. This is another big win for ‘theory.’ In recent years, the Sneddon equation has also been remarkably confirmed by the heart-shaped lobes of tension observed ahead of crack tips in offset fiber observations.
These results are reassuring because they show that our fundamental ‘fracture mechanics’ theory works, and that it is capable of reproducing the key behaviors of realistic systems in-situ. Pretty remarkable for a mathematical theory that was developed so long ago, dating back to the work of Inglis (1913). These findings remind me of the works of David Pollard, a professor at Stanford, who’s spent his career documenting how remarkably fracture mechanics describes the behavior of natural fractures observed in geologic outcrops. This stuff work!
Next up – Ge et al. (2022) had a great case study on RevoChem’s technology using geochemical fingerprinting to develop oil production allocations by layer. This is low-key one of the most important diagnostics to come out in recent years. By analyzing the chemical fingerprint of the oil, they can tell you the percentage of production in each well coming from each layer. This is extremely useful for designing wine-rack completions because we can assess the draining height of the fractures from each well.
In ResFrac, we’ve been getting this geochem data so often – and finding it so useful in our calibration work – that I recently implemented a new ‘oil soluble tracer’ module for use in the ‘black oil model’ so that we can calculate fully accurate flow allocations as a model output. Check this paper out – it’s a really important, high quality diagnostic!
Carrascal-Delgado et al. (2022) proposed a novel and interesting idea – rather than trucking off drill cuttings and having to dispose of them (which is costly and has potential environmental impact), why not mix it back into the frac fluid and reinject it back into the formation with the frac job? Based on their analyses, they argue that this will not impact proppant pack conductivity. If so, this would provide a neat way to reduce cost and environmental footprint.
Finally, Cozby and Sharma (2022) provide a really nice statistical analysis of parent/child impacts. In particular, they did a really nice job of identifying potential confounding covariates. For example, they look at relative performance of parent and child wells and find that for parent wells drilled prior to 2017, the child well performance is relatively robust, or seemingly unaffected by parent/child depletion. For parent wells drilled after 2017, child wells underperform much more. Why? Because from 2017 onward, the frac designs got much higher intensity. When parents were completed with lower intensity designs pre-2017, and then child wells were completed with higher intensity designs post-2017, the child wells were still affected by the parent, but this was masked because they had a relative uplift from their higher intensity designs. This comparison demonstrates the risks and potential pitfalls of data analytics on well-performance. It is a multivariate problem, with lurking covariates, and it is easy to arrive at spurious correlations. Cozby and Sharma (2022) wrote an impressive and sophisticated paper, especially considering that the first author wrote it for his senior undergraduate thesis at UT!
Ballinger, Bradley, Green, Brett, Vajjha, Pavan, Haffener, Jackson, Edwards, Mark, Almasoodi, Mouin, and Kyle Haustveit. “Understanding the Hydraulic and Conductive Half Lengths in the Bakken/Three Forks Play – Coupling Sealed Wellbore Pressure Monitoring SWPM & Chow Pressure Group CPG.” Paper presented at the SPE Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, USA, February 2022. https://doi.org/10.2118/209144-MS
Barhaug, Jessica, Bussey, Jacqueline, Schaeffer, Ben, Shemeta, Julie, Lawrence, Matthew, Tran, John, and Price Stark. “Testing XLE For Cost Savings in the DJ Basin: A Fiber Optic Case Study.” Paper presented at the SPE Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, USA, February 2022. https://doi.org/10.2118/209155-MS
Carrascal-Delgado, Fabián, Abedi, Sara, Hill, A. D., and Ding Zhu. “Feasibility of Using Drill Cuttings as Proppants in Unconventional Reservoirs.” Paper presented at the SPE Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, USA, February 2022. https://doi.org/10.2118/209173-MS
Cipolla, Craig, McKimmy, Michael, Hari-Roy, Stephanie, Wolters, Jennifer, Haffener, Jackson, Haustveit, Kyle, and Mouin Almasoodi. “Evaluating Stimulation Effectiveness with Permanent Optical Fiber and Sealed Wellbore Pressure Monitoring: Bakken Case Study.” Paper presented at the SPE Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, USA, February 2022. https://doi.org/10.2118/209129-MS
Cozby, Joe, and Mukul Sharma. “Parent-Child Well Relationships Across US Unconventional Basins: Learnings from a Data Analytics Study.” Paper presented at the SPE Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, USA, February 2022. https://doi.org/10.2118/209171-MS
Eckdahl, Rick, Vigrass, Adam, Singh, Amit, Liu, Xinghui, and Larry Chrusch. “Assessment of Limited Entry Cluster Distribution Effectiveness and Impactful Variables using Perforation Erosion Measurements.” Paper presented at the SPE Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, USA, February 2022. https://doi.org/10.2118/209122-MS
Elliott, Brendan, Zheng, Shuang, Russel, Rod, Sharma, Mukul, Haustveit, Kyle, and Jackson Haffner. “Integration of Sealed Wellbore Pressure Monitoring Responses with Wellbore Strain and Deformation Measurements for Fracture Diagnostics.” Paper presented at the SPE Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, USA, February 2022. https://doi.org/10.2118/209120-MS
Ge, Shuangyu, Kintzing, Malcolm, Jin, Muqing, Wu, Jiang, Bachleda, Jana, and Faye Liu. “Time-Lapse Monitoring of Inter-Well Communication and Drainage Frac Height Using Geochemical Fingerprinting Technology with Case Studies in the Midland Basin.” Paper presented at the SPE Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, USA, February 2022. https://doi.org/10.2118/209145-MS
Haustveit, Kyle, Elliott, Brendan, and Jon Roberts. “Empirical Meets Analytical-Novel Case Study Quantifies Fracture Stress Shadowing and Net Pressure Using Bottom Hole Pressure and Optical Fiber.” Paper presented at the SPE Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, USA, February 2022. https://doi.org/10.2118/209128-MS
Huckabee, Paul, Gustavo Ugueto, Kyle Haustveit, Magdalena Wojtaszek, Somnath Mondal, Chris Ledet, Talib Daredia, Alan Reynolds. 2022. Completions and Stimulation Experimental Design, Execution, Analysis & Application for the Permian Delaware Basin Hydraulic Fracture Test Site 2. Paper SPE 209172 presented at the Hydraulic Fracturing Technology Conference, The Woodlands. https://doi.org/10.2118/209172-MS
C. E. Inglis, “Stresses in a Plate Due to the Presence of Cracks and Sharp Corners,” SPIE Milestone Series, Vol. 137, 1913, pp. 3-17.
Ribeiro, Lionel, and Wesley Zurovec. “Practical Design Considerations for Perforation and Stimulation Strategy Based on Two Permanent Fiber Optics Tests in the Williston Basin.” Paper presented at the SPE Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, USA, February 2022. https://doi.org/10.2118/209183-MS
Snider, Phil, Baumgartner, Steve, Mayerhofer, Mike, and Matt Woltz. “Execution and Learnings from the First Two Surface Tests Replicating Unconventional Fracturing and Proppant Transport.” Paper presented at the SPE Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, USA, February 2022. https://doi.org/10.2118/209141-MS
Watson, Mark, Schinnour, Mitch, Cramer, David D., and Matt White. “Driving Completion Execution Improvements Through Detailed Analysis of Acoustic Imaging and Stimulation Data.” Paper presented at the SPE Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, USA, February 2022. https://doi.org/10.2118/209184-MS