Hydraulically fracturing operations is becoming much more complex as the gas formations are being depleted with the time. In addition to this, some gas reserves need to be recovered by fracturing horizontal wells with multiple stages which is the case of an extensive gas field in the Sultanate of Oman that has been producing since 1991 mainly by hydraulic fracturing. The scope of this paper is to discuss the different methodologies in the operations associated to hydraulic fracturing in horizontal gas wells with formations depleted in PDO, the main objective is to show operations and well delivery improvement by the optimization of tools conveyance, perforating techniques, clean out and milling strategy. The paper will show the enhancement of the operations and the outstanding results in these challenging well conditions. The paper will start by describing the different methods used to execute operations for fracturing horizontal wells which are mainly related to plug and perf technique, clean out and milling plugs in between stages. Further, it will discuss the strategy, planning and job execution of one of the wells with 14 stages in the horizontal section, the perforating technique and strategy used to help reduce screen out's, it will also discuss the acquisition of spectral Noise log data post fracturing with the assistance of Nitrogen as well as the milling of the isolation plugs at the end of the job. The optimization of the conventional operations is a novel approach to enhance hydraulic fracturing in depleted horizontal gas wells in PDO, this is in alignment with the continuous improvement ideas and the lean thinking across the oil and gas industry. It is easy to replicate in other horizontal wells to be hydraulically fractured which will reduce cost, HSE exposure and will help increase the recovery of hydrocarbon reserves.

The scope of this paper is to discuss the methodology to perforate deep High pressure, High Temperature (HPHT) gas wells that are completed with permanent fiber optic behind-casing for hydraulic fracturing operations in Petroleum Development Oman (PDO), the main objective is to show the planning and successful execution of perforating and hydraulic fracturing operations in this new type of completions. The paper will show the enhancement of Well Delivery and the outstanding results in these challenging operations. The paper will start by elaborating on this new type of completions with permanent fiber optic, the benefits, and the challenges associated to perforate the casing while maintaining the integrity and functionality of the fiber optic throughout all the hydraulic fracturing operations. Different orienting tools, gun sizes, shaped charges, explosive types, and gun phasing were evaluated and assessed to achieve the optimum system. Yard tests were done with an actual casing joint and fiber optic. Further, it will discuss the design, planning and successful job execution in one of the new gas wells with 4 fracturing stages completed. Field operations were successfully executed in a deep gas well with 4 frac stages using plug and perf technique, the optimum and novel perforating system allowed to complete a total of 24 perforating runs without any damage to the permanent fiber optic behind-casing, it also allowed to successfully initiate and propagate the fracture in all stages. A final multi finger Caliper log also indicated that there was no tubing damage or deformation across the perforated clusters after milling all the frac isolation plugs. The well was successful delivered to production operations. The concept of perforating and fracturing deep gas wells completed with permanent fiber optic has been proved with substantial benefits, not only for the hydraulic fracturing operations but also for future Well Reservoir Management (WRM) and surveillance activities through the life cycle of the well. Perforating and hydraulic fracturing in wells completed with permanent fiber optic is a novel approach to enhance hydraulic fracturing and well delivery, this is in alignment with the continuous improvement (CI) ideas and the lean thinking across the oil and gas industry. It's easy to replicate in other gas and oil fields, as well as horizontal wells to be hydraulically fractured, it will reduce cost, Health, Safety & Environment (HSE) exposure and will help increase the recovery of hydrocarbon reserves.

Casing deformation has been detected in Oman's deep gas wells after hydraulic fracturing, particularly in Saih Rawl (SR) and Burhaan (BRNW) fields across Miqrat and Barik units. Hydraulic fracturing is a key enabler for the development of these reservoirs, understanding the conditions that lead to casing deformation after fracturing, is fundamental to define strategies to operate, reduce or eliminate its associated impact over well integrity and final hydrocarbon deliverability. The casing deformation was observed following fracture operations across the target intervals. The deformations were localized in the pipe body and not in the connections, and they were identified as week points. The deformations were characterized by the ovalization of the casing, covering approximately 1 to 2 meters length along the pipe. These deformations could lead in some cases to the complete burst of the tubular or further damage as a result of plug milling operations. A holistic approach was developed, following the QA/QC of gathered key data, combining the review of multi-arm caliper data, detailed geomechanical properties profiles, mini-frac analysis, camera imaging and casing integrity analysis under the anticipated fracture loads; this covering 3 vertical wells and 1 horizontal well, where deformation after fracturing was clearly detected. Following this combined review and the detailed evaluation of the operational events in each of these wells, it was possible for the first time to identify a correlation between variability of geomechanical properties, fracture propagating pressures and the observed casing deformations. It will be presented how a strong correlation between high contrast in Young's modulus, with high net pressures observed during fracturing, was identified. It will be also discussed how this deformation occurs in 2 to 5 meters thickness zones, correlating to sharp changes in Young's modulus and high instantaneous shutting pressure gradient, observed during the mini-frac stage. All the prior conditions need to be present to create the circumstances that could lead to casing deformation. It is also clear the need to study in more detail the dynamic interaction between the fracture propagation, rock displacement and casing deformation, in order to enhance the completion, perforation and fracture strategies to prevent or manage this deformation. However, as our understanding has improved, we can now define strategies to reduce the risk and prevent further deformations; these strategies will be shared and discussed. It is necessary to have a holistic approach to go beyond the analysis performed by using casing strength analysis, to assess the loads imposed during fracturing. It is required to incorporate the interaction of the fracture loads induced -during its propagation- into the formation and the ones generated by the pressure and temperature profile in the completion during fracturing. With the understanding on the conditions that lead to casing deformation in these fields, it was possible to define strategies that can reduce the risk and prevent deformations. Lessons learned can provide knowledge to reduce the impact over well integrity and hydrocarbon deliverability, obtaining improvements in production gains in such tight formations.

The scope of this paper is to discuss and compare the different milling strategies of the frac plugs associated to hydraulic fracturing operations in both, vertical and horizontal gas wells, with formations depleted in Petroleum Development Oman (PDO); the main objective is to describe milling operations and the well delivery improvement by the optimization of clean out and milling strategy. The paper will show the enhancement of the milling operations and the outstanding results. The paper will start by describing the execution of hydraulic fracturing operations in both vertical and horizontal wells, which is mainly related to plug and perf. It will also cover clean out and milling practices for frac plugs in depleted formations. Further, it will discuss the planning and design of the post frac clean outs and milling jobs based on the learnings previously captured. Frac plugs milling operations have been successfully improved in severe depleted vertical gas wells and some horizontal wells with no severe depletion; initially the milling operation was done after all frac stages were completed in depleted wells, out of the critical path, however the experience showed that it was a lengthy and expensive process due to the severe formation losses while milling leading into a very low efficient operation impacting the frac well delivery. The subsequent step was to address the milling after every stage, during the critical path, which increases the cost of daily frac charges. With the use of an innovate downhole technology the milling strategy was changed and optimized showing outstanding results, milling frac plugs was achieved successfully at the end of the job in horizontal wells while in some previous wells the milling was done in between the stages; also for vertical depleted gas wells, fracturing stages have been combined to mill frac plugs together. The completion of the entire wells (well delivery) was achieved in a relative shorter period of time compared to previous wells; this is reflected on actual cost reduction of more than 20% of total cost/AFE The optimization of the frac plug milling operations is a novel approach to enhance hydraulic fracturing and well delivery in depleted gas wells in PDO, this is in alignment with the continuous improvement (CI) ideas and the lean thinking across the oil and gas industry nowadays. It is easy to replicate in other gas fields expected to be depleted, which will reduce cost, Health, Safety & Environment (HSE) exposure and will help increase the recovery of hydrocarbon reserves.

Saih Rawl gas is located in the South Oman Salt Basin. There are two main formations targeted for gas production; Barik & Miqrat Formations. These formations are tight and exhibit low permeability. In order to enhance gas production, these formations have to be hydraulically stimulated. The main objectives of this paper is to demonstrate the petrophysical properties of the hydraulically fractured zones. Assess gas flow contribution thru the individual zones measured by production logging and comparing with the amount of proppant placed in the formation. In addition, the paper discusses reservoir properties and characteristics obtained from logging, post stimulation operations results and post stimulation gas production. The paper discusses 20 wells; 10 from the crest and 10 from the flank. The two formations Barik and Miqrat cover approximately 17 sub reservoir units. The total overall placement ratio is 95% and 78% for the crest and flank respectively with 156 hydraulic stimulation stages. It was observed that five sub reservoir units proved to be challenging to place the desired proppant. The maximum operating pressure is reached before achieving the desired proppant concentration leading to a screen out; concentrations of 2 – 3 pounds per gallon. Petrophysical evaluation of porosity and permeability cross plots showed a linear relationship in the wells in the crest. While there was no clear relationship was seen in the flank. Radioactive tracers used are to understand if there is any proppant propergation into the higher or lower zones. Not all the five challenging sub reservoir units showed propergation to other units. The wells located in the crest showed a better production rate as compared to the flank. The paper highlights the importance of the using petrophysical evaluation to optimize hydraulic fracturing design for successful operations.