The proposal of this paper is to share the knowledge learned in this new procedure and techniques implemented in HP/HT Unconventional wells, created by the Unconventional (UC) Drilling Department at Abu Dhabi which involve around ten different services, where each has a high importance and contribution for the collective success of the well at the moment to frac and hence the feasibility of the project. In order to assure the integrity and accessibility of the Frac String during Plug and Perf hydraulic fracturing operations of one of the toughest rock in Unconventional business worldwide, one procedure has been developed for running operations best practices. Pressure testing the Frac String (FS) during running in hole in stages while in vertical section to sure safe and successful Wireline setting and retrieving nipples plug with more than 30% solids in the system (high mud weight) to guarantee no leak in the string prior reaching total depth (TD). Hanging and testing cross over (XO), assuring compatibility with the wellhead connections. Cementing up to18.7 ppg. Flexible and expandable slurries, cement inside previous casing and apply pressure on surface to avoid gas percolation during the cement setting period. Cleaning out with Coiled tubing (CT) to ensure no obstruction and using different completion fluids for future accessibility. And finally, Pressure testing the Frac string up to 14ksi all are new practices and proven mitigation measures for all assessed risks for hydraulic fracturing operations. This paper is about sharing this new procedure in Abu Dhabi for having a cemented FS in UC wells High Pressure / High Temperature (HP/HT) with 100% integrity and internal accessibility to run plugs, perforations, logs and be able to apply high surface pressure to frac the tight reservoir in the planned zone, creating the desired permeability for future production.

For the past few years ADNOC has extensively ramped up its effort in exploring and testing unconventional reservoir across Abu Dhabi tight oil and shale gas formation as part of its oil & gas 2030 strategy. Shilaif tight oil exploration started over 5 years ago with multiple vertical wells drilled and tested allowing discovery of stacked tight oil play with significant resources in place. To unlock these resources, horizontal drilling and multistage fracturing were used to confirm recoverable resources, and well potential. Prolific production results have since propelled hydraulic fracturing, hence it has become imperative to build a process to standardize unconventional fracturing technical and operational requirements and to maximize efficiency and benefit. A prime example of such process was in Huwaila-68 where the organic-rich Shilaif shale/tight oil formation was targeted. A target that is analogous to the Eagle Ford from the same Late Cretaceous age. A significant weight is put on reservoir quality assessment to minimize margin of error and increase the probability of fracturing success, and to maximize recovery of the estimated tight oil and shale gas in place. This process assessed the Shilaif from a geological, petrophysical, and geomechanical perspectives. This was followed by setting up preferential staging and perforation placement strategy for fracturing based on reservoir and completion quality which correlated to an initially built 1D mechanical earth model. Production forecasting using reservoir simulations were also utilized to assess fracturing success and deliverability. The processes above led to completing multistage fracturing in Huwaila-68 within the Shilaif formation by means of a pump- down perf and plug operation coupled with high rate slick water pumping, which was followed by extensive well testing. Operational efficiency allowed for the completion of 27 stages placing in excess of 7.3 million lbs of proppant. The use of chemical tracers as a qualitative measure allowed for correlation between natural fracture presence, recorded pumping events, and initially recorded gas shows while drilling. Such observations would help in well placement for future horizontal wells. Post fracturing production rates have met expectations, and were in line with the initial reservoir assessment predictions. The novelty of this paper is the inclusion of several domains to reduce the error margin of fracturing unconventional formations such as the Shilaif. Being an area where field development is rapidly taking place, the inclusion of new technologies have become persistent, and these were evident from the reservoir assessment phase, through to the fracturing phase, and ending with the well testing phase. This level of data gathering and assessment will act as a benchmark for all future unconventional fracturing within the UAE while lessons learnt will further enhance the turnover from drilling to production.

The purpose of this paper is to share the results and knowledge learned in implementing new procedure and techniques to rotate the 5-1/2", 26 PPF, T-95/P-110 Frac String (FS) during running into Unconventional wells. Developed by ADNOC Onshore ASR - UC Drilling Department at Abu Dhabi (U.A.E.) the novelty involves six (06) different technologies necessary to minimize axial buckling in the monobore completion while maximizing well accessibility and integrity during the Rigless frac operations. The 6 key enablers technologies employed to rotate the Frac String up to 30,000 pound-ft: Connection: strength to withstand rotation required to release the axial buckling.High Speed Reamer Shoe: open hole debris cleaning / obstruction removal.Bonded Ceramic Centralizers: providing 80% standoff, reducing the friction factor and removing the mud cake with the rotation.Casing Running Tool: designed to wash down and rotate FS during running.Rotating Tubing Hanger: enabling FS rotation using different techniques and design a new mechanism for it after landed and locked into the Tubing Head Spool.Rotating Cement Head: ability to rotate the FS while pumping cement and plugs simultaneously. Because of friction, sliding during running will result in helicoidal buckling of the FS that has a negative knock down effect on later completion operations / interventions and even in some cases not possible to reach the TD. The results of previous UC wells where FS was run in sliding mode revealed issues due to the helicoidal buckling of the FS impairing annulus / cement bond quality, creating tortuosity and altering the Internal Diameter (ID) leading to issues in accessing the well bore with the Plug and Perf tool for the fracking operations. The total depth for standard UC wells ranges from 16,000’ to 23,000’ MD with ± 12,500’ TVD and ± 8000’ MD 8"1/2 horizontal section dipping up to ±92° inclination for production reasons. Such profiles generate Friction Factor (FF) ± 0.5 in Open Hole. Based on performed simulations and depending on the well profile, surface torque required to rotate the string was between 25,000 to 30,000 pound-ft. This paper will describe and provide details on how the FS helicoidal buckling was minimized and its limitations overcome thanks to the six key enablers technologies devised by Onshore ASR - UC Drilling Department. It will also highlight other important added benefits such as mud cake removal, improved annulus geometry and cement bond.

This paper undertakes the application of Pressurized Mud Cap Drilling (PMCD) technique with Manage Pressure Drilling (MPD) as a new drilling approach in the Unconventional Gas Exploratory field to successfully drill through Nahr Umr & Shuaiba formations managing the risks associated with total losses due to the natural fracs and faults in the area, which if drilled conventionally instigate well control situations, large amount of drilling fluid lost into reservoir and not reaching the target depth (TD). One of the most powerful drilling techniques to apply in unconventional wells is MPD, It's used to optimize drilling operations under critical challenges, such as narrow window between pore pressure, hole instability and fracture pressure, pressure heterogeneity when drilling different formations and severe downhole losses. Study was carried out to mitigate challenges across 8-½" and 6″ holes based on previous conventional drilling experiences of simultaneous kick and loss events, MPD system was introduced to overcome that challenge. When severe losses were encountered at Nahr Umr & Shuaiba formations PMCD, an MPD technique, offered the ability to reach well TD despite the total losses using 3 different drilling fluids, Sacrificial fluid (SAC), Light Annular Mud (LAM) and Kill Mud Weight (KMW) in closed-loop drilling without mud returns while stablishing a mud cap in the annulus managing the wellhead pressure by bullheading to stop gas migration. PMCD facilitated drilling under suddenly total losses minimizing the mud consumption, reduced time/cost and avoided un-controlled release of hydrocarbons. Four wells were successfully drilled, for a total of 1,183 ft, under severe Losses where LCM treatment could not heal the natural fracked formation. PMCD converted conventional drilling into close-loop drilling system by installing Rotating Control Device (RCD) on top of the annular Blow out Preventer (BOP) establishing mud-cap in the annulus and allowing constant monitoring of the well conditions via Surface Back Pressure (SBP). A positive injectivity test was performed after total losses to confirm the formation can take drilling fluid and cuttings. Drilling started with SAC injection in the string and LAM injected intermittently in the annulus through the RCD, whenever the SBP required to be managed due to gas migration effect into the mud cap. Tripping out of hole the drilling BHA and running completions were performed in PMCD mode. This paper is the number four written (Previous: SPE-207798-MS, SPE-211775-MS & SPE-211775-MS) for the milestones achieved to develop this new area with Geo-political strategic for UAE. Apply the PMCD, helped to reduce the time of drilling & completion in the UC wells, due to the losses control, from 35 days in average to 10 days, and saving ± 50% of the budget in the target sections (8-1/2″ & 6″).

In a current oil & gas challenging drilling environment where the fields are becoming very congested, PAD drilling and field grid designs with close proximity wells operation is booming. Drilling challenging wells with high collision risks is common as a result of the requirement to maximize the Asset value of the oil fields. For this reason, the urge for ensuring accurate well placement is becoming critical and as a result high technology methods are required to be in place. Developing new areas where the poor and/or inaccurate drilled wells information (most of them are vertical) affect planning and placement of new wells due to the uncertainty in existing wells trajectories, causing collision issues among the new planning and the "trajectory" of the existing wells, leaving huge quantities of reservoir volume not possible to drain. For this study case, where the reservoir has some complexity due to faults and water, such limitation is critical. The analysis and fusion of new techniques and procedure to manage the risk for the collision were implemented. Directional tools with high level of accuracy measurements were deployed and stringent procedures are put in place. The Analysis, Logic, Considerations, Mitigations, Risk Assessments and a New Procedure implemented to avoid collision issues while drilling horizontal wells with Separation Factor (SF) less than 2 (standard worldwide is equal or above 2 and for this case, it was 0.6). This was developed by the Biogenic / Unconventional team, Drilling Department of Abu Dhabi National Oil Company (ADNOC) Onshore with the support of drilling service company and the approval of the ADNOC Head Quarter, to take advantage of around 0.9 km2 of hydrocarbon area for future drain. The well was drilled successfully and safely, no collision or magnetic interference issue in any trajectory survey were reported during drilling and passing close by the existing well.