Economical hydrocarbons production from unconventional resources is intrinsically related to stimulation effectiveness and capacity of the created hydraulic fractures to drain the target resource in an efficient manner, this is certainly without overlooking the significance of other resource geological, petrophysical, geomechanical, and other rock quality aspects. Considering the unique characteristics of each unconventional resource and the varying rock qualities and geological features, each resource should be considered separately when attempting to define the most optimum stimulation design approach that yields the best well productivity results and best EUR's, this means that a stimulation design approach that was successful in a specific play might not yield the same success if applied in a different play. In general, the overall stimulation effectiveness in unconventional horizontal multi-stage completions requires a good understanding of the geological, petrophysical, and geomechanical characteristics of the asset in hand as well as an understanding of the natural fracture's distribution, rock heterogeneity, and other aspects, eventually integrating those understandings to design an effective stimulation approach that similarly considers cost and operational efficiency parameters. Efficiency of the stimulation treatments requires an optimal placement of perforation clusters, with reasonable spacing that allows for creating the target fracture geometry/complex fracture network while considering fracture interferences, and other geometry controlling aspects. One of the most important considerations when designing a fracture treatment is fracture conductivity which is the ability of fractures to convey produced fluids into the wellbore (fracture permeability multiplied by fracture width (md-ft). In general, fracture conductivity along the created fracture network as well as in the near-wellbore area defines how effective is the fracture in delivering hydrocarbons into the wellbore, the target fracture conductivity values however vary with respect to formation rock permeability ranges and nature of produced fluids. This paper presents a comparative study of fracturing design and operational execution approaches for two exploration wells drilled in the oil-bearing Shilaif unconventional formation in the UAE, both wells are drilled targeting the same rock sequence and both possess very similar rock qualities. The paper covers aspects studied to analyze the suboptimal performance of the first well and the adjustments made to the fracturing design and fracture conductivity improvement of the second well, and how it entirely changed the productivity profiles and significantly improved the EUR for the target resource, which in turn had made this asset much more attractive for future full development plans.

The proposal of this paper is to share the case history and knowledge learned in this first application of the multistage zipper frac procedure and techniques in Biogenic wells. This breakthrough achievement was planned and executed by ADNOC Onshore Biogenic Drilling Department in Abu Dhabi which involves seven different services, each has a high importance and close collaboration was a key contributor to the feasibility of the project and the collective success obtained. The Zipper frac method selected and tailored by the Biogenic Team for the specific application enables to significantly increase the number of fracs per day performed over 2 wells. This technique stages multi-well completions, where wells are completed in a back-and-forth manner. One well is being pumped /fractured while the other well is being plugged and perforated for next stage. One of the key achievements in the Biogenic Zipper frac operation lies in the easy switch from line to another by using a manifold in a safe manner and without confusion. Because of the focus and high potential of Biogenic gas, Biogenic Team faced the challenge of delivering the two wells on a very tight schedule. This led the Team to review, select and implement a novel methodology that would deliver time and cost savings to the Project. New ideas were scouted and analyzed by different departments and service companies to select the most appropriate. Upon selection of the zipper frac method, meetings were done to issue and finalize a proper implementation plan for this multi-frac operation, which was a first in ADNOC Onshore. Explaining in workshops to key stakeholders and respective higher management the methodology and plan as well as the associated savings was essential to get full support and endorsement for implementing this method. There was no doubt that this method was the best way to achieve the goal with the tight given timeframe. Successful implementation resulted in of around 50 days savings compared with applying the conventional multiple frac procedure / method on a well-by-well basis. Wider application of this method represents a breakthrough in delivering future fracked wells cheaper and faster thereby bringing significant savings to future Biogenic gas development projects. Because of the importance of ongoing assessment and potential future development of Biogenic gas and unconventional resources, sharing details of ADNOC Onshore first implementation of the Zipper frac methodology is of benefit to the industry. The detailed account of its implementation (inclusive of added important technical features such as dissolvable plug and perf technology) that has delivered safely and successfully twenty-four (24) staged fracs in a short time frame represents a piece of useful knowledge.