Deep gas drilling in carbonate environment is very challenging due to elevated temperatures with pressures. Additionally, the presence of the shock and vibrations across the interbedded layers of limestone and dolomites. Over the years different drilling techniques are employed for improving the drilling performance. The analysis of the data showed that the wells where the shock and vibrations were lower the optimum performance was achieved and the section was drilled in one run compared to the wells where multiple runs were required because of shock and vibration. Further analysis showed that the Shocks are not only seen while drilling, but the level of shocks was high during non-drilling activity such as reaming during wiper trips, back reaming across tight spots and before reaming while connection. This paper will cover the techniques that were employed to minimize the S&V or at least reduce to the minimum acceptable level where the drilling performance can be achieved. Understanding the shock and vibration across different formations and sub layers within formation. Comparison of shock and vibration for different BHA's while drilling. Application of the stat of the art drilling dynamic simulator. Comparison of BHA's with standalone and motor power Rotary steerable system. Identifying and developing the strategy while crossing the interbedded layers. Feedback to the reliability team for improvement. Based on understanding the shock and Vibration, and lesson learned multiple wells are drilled where the number of BHA's used to drill the section are reduced and the ratio of drilling the section in one runs is increasing.

Generally, deep gas workover/re-entry wells in Saudi Arabia are kicked off in the Sudair formation through a whipstock because the overlying base Jilh dolomite can flow with high pressure, which jeopardizes well control. Whipstocks are set deep in the 9 5/8-in. casing, after which the 8 3/8-in. and 5 7/8-in. holes are drilled to access the target Lower Carbonate and Sand reservoirs. Deeper kickoffs also avoid contact across the water-bearing Carbonate A, aiming for displacement across Carbonate B or C reservoirs. Isolation from Carbonate A is important for multistage fracturing completions as they are still not proven for the long-term isolation of water-bearing zones. Regardless of the deeper whipstock setting, the high dogleg requirements exceed the capabilities of conventional rotary steerable systems (RSS). Conventional steerable motors with high-bend housing and 70 to 80% of the sliding mode of drilling has been the only option to achieve such high dogleg severity (DLS/100ft). Drilling medium-radius wells with a conventional motor assembly requires multiple runs, wiper trips to clean the hole, and multiple reaming trips before running the liner. These operations result in poor drilling efficiency due to slow penetration rates and bit trips. A high build rate rotary steerable system (HRSS) was introduced as a solution for such challenges in the 8 3/8-in. and 5 7/8-in. sections. While the HRSS technology has been used before, this was the first time the HRSS kicked off vertically from a whipstock in Saudi Arabia or worldwide. The new technology allowed the kickoff point to be pushed further into the Sudair formation near the Sudair dolomite, reducing the risk from Jilh pressure and associated cost. The step change provided the option to slim the hole by eliminating the 8 3/8in. hole size, and kickoff was done in the 7-in. liner. Deployment of the HRSS allowed directly kicking off from a whipstock set vertically, eliminating the need for a dedicated steerable motor assembly run. Direct kickoff also meant eliminating the need for gyro tool for steerability, because conventional RSS tools could only be used outside the zone of magnetic interference, once sufficient separation from the mother bore was achieved. Consistent doglegs of more than 14°/100 ft were recorded; and the maximum dogleg was 17.44°/100 ft. Since then, this concept has been applied to other vertical re-entry wells and at an existing inclinations successfully in the 8 3/8-in. and 5 7/8-in. sections in Saudi Arabia and worldwide. The scope of the paper is limited to wells in Saudi Arabian deep gas wells only. The average rate of penetration (ROP) across this build section shows a 137% improvement over the ROP for conventional motor bottom-hole assemblies (BHA) for similar build sections. Eliminating the 8 3/8-in. section, avoiding the hazards of drilling in Jilh and Sudair formations, saving the motor trip to kick off from the whipstock, and improving ROP resulted in significant savings. This step change in drilling performance was realized by a thorough understanding of local drilling conditions and indepth analysis that enabled efficient execution.

Combination of well design practices, geo-steering with neutron-density and multilayer bed boundary mapping tools with a motorized rotary-steerable service (RSS) bottom-hole assembly (BHA) has been successfully used in the Ghawar field to accurately detect multiple formation layers enabling drilling performance improvement and optimized well placement services in challenging carbonate wells. The objective of the work-over program is to establish water-free gas production from the reservoir, especially as the gas-water contact (GWC) rises with on-going production. The Ghawar field is located in the eastern part of Saudi Arabia which contains non-associated gas in the target formation varying greatly in depth from the North and South of the field. The target formation consists of major gas bearing intervals, known as Carbonate Layer A and Carbonate Layer B. The Carbonate Layer-A averages about 120 ft in gross thickness and consists primarily of dolomite capped by anhydrite. The Carbonate Layer-B formation, like the Carbonate Layer-A, consists mainly of dolomites capped by tight anhydritic dolomites. In addition, these wells are drilled in the minimum horizontal stress directional for the advantages of optimized hydraulic fractures during stimulation phase and thus improved productivity. But these wells are notorious for stuck pipe risks, tripping difficulties and slow drilling penetration rates (ROP) with high shocks and vibrations. These risks are primarily due to geo-mechanical wellbore instability and uncertainty in both GWC depth and reservoir pressures arising from the strategy of drilling through multiple layers. With very low contrast in resistivity and the complex nature of the targeted reservoir, steering with only resistivity contrast using conventional bed boundary techniques would not suffice. Ideally, steering in a single layer of the target formation will eliminate the risks associated with the traditional steering method of passing multiple layers. Neutron-density combined with a new multilayer bed boundary mapping service were successfully deployed in deep gas Udhailiyah on four different wells. This service provided precise delineation of targeted reservoir layers in addition to giving an estimate of formation dip resulting in faster and more accurate geosteering. Steering effectively in these complex thinly bedded reservoir layers has shown improved drilling and tool reliability indicators, including incremental ROP improvement, zero stuck-pipe incidents, stick-slip and shock reduction, and the confidence to push with maximum parameters with a motorized RSS BHA to minimize open hole exposure and avoid borehole deterioration effects with time.

In the past two decades, the point-the-bit rotary steerable system (RSS) has been widely used for high-profile directional drilling jobs in challenging environments, which require accurate directional control. A new inertial steering mode of the point-the-bit RSS was developed by using accelerometers and a rate gyroscope sensor to achieve toolface control in environments, where magnetometers cannot be used for steering. This inertial steering mode effectively expands the operational envelope of point-the-bit RSS by improving its steering ability when magnetic interference, such as drilling out of whipstock window and close to offset wells or ferrous formations, is present or within a Zone of Exclusion (ZOE). Furthermore, the new steering mode can be used as a redundancy scheme in circumstance during magnetometer failures. Through close collaboration between Research and Development (R&D) and field operation, the inertial steering mode of the point-the-bit RSS has been successfully applied in four wells in Middle East oilfield. In the first well, the new steering mode was used to kick off two 8 3/8" hole sections after setting whipstocks in near vertical wells and it completed the kick-offs in desired directions with accurate toolface control in a high magnetic noise environment. In the second well, the new steering mode was used to exit the casing and drill to TD by using a whipstock. In the third and fourth wells, 12 ¼" hole sections passing through the ZOE were successfully drilled according to the well plan. The application of the new steering mode in these wells saved extra BHA trips, which would have been required if without this new steering mode. The successful application of the new steering mode in the Middle East oilfield has proven its technical advantages and business benefits.

High frequency torsional oscillation (HFTO) is still one of the most disruptive drilling dysfunctions we encounter. Vibrations are observed with fundamental frequencies as high as 400 Hz and torque sweeps from 0 to 7000 lbf.ft. The resulting damage includes drilling collar cracking, damaged electronics, and backed-off tools. By measuring the amplitude and the fundamental frequency of this dysfunction, we present a model to characterize its drivers. This is a critical step in defining the mitigation strategies. Although there are a multitude of drilling dynamics tools deployed to record these effects, the nature of HFTO, with large amplitude harmonics on top of the fundamental modes, means that simply deploying a sensor and data acquisition tool is not sufficient to characterize the dysfunction. There are critical requirements for these recorders in terms of sampling frequency and anti-aliasing filters, without which a unique interpretation of the dynamics is impossible. We have a next-generation MWD tool that will detect HFTO. By calculating a fast fourier transform (FFT) in real time, it will also deliver a log of HFTO throughout the operation, that can be delivered to the driller in real time. With this we have developed and demonstrated a suite of mitigation strategies. These are specific to the type of HFTO detected and include increasing the collar speed or reducing the WOB (for Type 2) or reducing the rate at which the WOB is increased (for Type 1). We also show that by changing the contact points on the tool to reduce the side force (friction), the operator can mitigate the Type 2 HFTO and achieve a considerable improvement on this drilling dysfunction and its impact.