Historically, vertical wells were used to correlate formation tops and determine the lateral continuity of the reservoir. With the advancements in horizontal drilling and logging, the industry is able to gather an immense amount of information about the rock as we drill farther away from the vertical section. Numerous industry publications indicate that approximately 40% of the perforation clusters in hydraulic fracturing do not contribute to production. Many factors play a role in such production behavior, but the most important factor is the breakdown of perforations and propagation of the hydraulic fractures through them. Several methods, such as limited entry design and placing perforations in similar type rock, have been applied to mitigate this problem; the information needed for these methods is obtained from logging the laterals or using drilling data to determine rock properties. Diagnostic tools such as production logs, permanent downhole fiber optics, radioactive tracers, and chemical tracers have been deployed to understand the varying production profiles seen across the unconventional reservoirs. This study focuses on three wells with lateral measurements to obtain petrophysical and geomechanical rock properties (one well in the Wolfcamp B and two wells in the Wolfcamp A). The wells also had pseudo rock properties calculated using surface drilling data. In most instances, the perforation clusters in each stage were placed in good reservoir and completion quality rock with the aim to minimize the stress differential between clusters. Different perforation schemes were tested in each of the three wells - number of clusters and spacing, limited entry, and geometric design. The wellbore geosteering profile, whether in or out of zone, was also considered in relation to the subsurface structure. Lateral measurements in all wells showed the changing lithology and rock types across the lateral. The Wolfcamp B had a production log that indicated twice as many clusters contributing in the section of engineered perforations compared to the section where the perforations were placed using the gamma ray log. Time-lapse chemical tracers in other wells indicated changing production profiles. For example, early in the life of a Wolfcamp A well, the stages with clusters picked based on logs showed the highest production contribution compared to the geometric stages, but, later, the trend started to shift in favor of the geometric clusters. The geometric stages were in an area of the wellbore where the carbonate content was highest. Comparisons of various data sets to production performance, such as the one included in this study, will provide some insight into the heterogeneous nature of the Wolfcamp shale and the impact of varying perforation techniques on production contribution from individual clusters.

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Methods for analyzing surface pressure data in real time are proposed and demonstrated to improve the completion design and cluster efficiency of child wells while protecting nearby parent wells. This study involves three parent wells and ten child wells, landed horizontally in the Wolfcamp A and B reservoirs in the Delaware Basin. An integrated real-time analysis of surface pressure measurements acquired from parent and offset child well completions enabled informed decisions regarding pump rate, fluid volume, frac stage sequence, and diverter schedule on subsequent stages. Results included the mitigation of frac-hits at the parent wells and improved fluid distribution of the child wells. Real-time monitoring indicated significant fluid communication during treatment between child and parent wells. The order of operations and completion design were changed during the job to reduce the risk of adverse effects on both well types from frac hits. By changing the treatment design, the magnitude and characteristics of pressures observed in the parent well showed significant reduction in the intensity of fluid communication. The design change also improved cluster efficiency of the nearby child wells, with no indication of damaging frac hits occurring. Pressure-based fracture mapping was used to supplement observations from the parent well. These pressure responses, recorded from an isolated stage on an offset well, were used to compute fracture geometries and growth rates of the stimulated fractures. The fracture height of the child wells decreased after adjusting the order of operations and completion designs during stimulation, which indicated fracture containment within the target zone. These results validated the improved cluster efficiency findings. The differences in geometries and growth curves were interpreted as improved fracture quality near the wellbore, with no damaging frac hits from the completion stages. Real-time pressure monitoring and analysis provides immediate, accurate feedback during stimulation. Data-driven decisions enables optimization of the frac design and pump schedule (slurry rate, slurry volume, proppant volume, proppant concentration, etc). Comprehensive understanding of the fracture growth behaviors assists in making more-informed decisions during the execution of a well stimulation program, mitigates parent well damage, and enhances child well production.

Recent industry analysis based on publicly available production data of most unconventional basins in the US have consistently highlighted the underperformance of child wells as compared to parent wells, although completion practices have continuously evolved. Industry publications have suggested that average productivity degradation of child wells can be up to 29% for some Delaware Basin operators. In some cases, the detrimental effects of parent-child relationships have also been observed on the parent wells after the stimulation of the child wells. In such an environment it is important to develop completion strategies to mitigate the negative effects of this parent-child relationship. In the Delaware Basin, the negative parent-child effect was successfully mitigated on two different zipper pads, with parent wells as close as 500 ft away from the zippered child wells. On the first pad, one parent well was completed and six months later two child wells were zippered with the closest child 1,000 ft away from the parent and pumped with far-field diversion. On the second pad, one parent well was completed and four months later three child wells were zippered with the closest child well 500 ft away from parent and far-field diversion pumped on the two closest child wells. The stimulation treatment design was carefully designed to include far-field diverters on the stages near parent wells. Job size and far-field diverter quantity were determined using an integrated hydraulic fracture simulation software with an advanced particle transport model. Contingency scenarios were also prepared to facilitate real-time changes required when or if abnormal behavior was observed during the execution. The zipper sequence was also planned to help establish a stress-shadow effect near the parent well to further mitigate detrimental parent-child interactions. To monitor execution in real time and evaluate interactions between wells, high-frequency pressure gauges were installed on all observation wells including parent and child wells. The completion design and far-field diversion treatment worked as planned for the first pad, with no significant well interference pressure signature observed on the monitoring well. For the second pad, the parent well saw pressure increases up to 700 psi during the treatment of a stage midway along the lateral of the closest child well which was completed with far-field diverter. Contingency plans were successfully executed, and no significant pressure increase was observed on the remainder of the lateral. Early production results indicate that the negative impacts of parent-child interactions were successfully mitigated on both pads, with the production of the parent wells quickly returned to their observed trends prior to child wells stimulation. Child wells production, when normalized both by lateral length and stimulation size, was on par with that of the parent well.