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.

Since the foundation of the oil industry, many wells were drilled with an old design. Such wells had been limiting the reserve recovery potential. In extreme cases, some of these wells had been suspended and remedial work is now required to unlock the wells’ potential. This paper presents a case study for restoring production and increasing the salvage value of suspended wells in areas with proven production potential yet declining production yields. Challenges for drilling the well were found in three key areas: Sidetrack Points: The main concern in this well was the failed cement job in the 9-5/8 in. casing and the pressurized formation above the targeted reservoir that had the potential to create new fluid paths through cement channels. The pressurized formation required a very heavy mud weight of 152 pcf and managed pressure drilling (MPD) to drill the previous well and incurred losses at the same time. By increasing the depth of the sidetrack point and drilling a short radius 5-7/8 in. wellbore in less than 200 ft., the risk of the pressurized formation communicating to the new lateral was eliminated. This saved the cost of drilling two hole sizes and the cost of milling approximately 1,500 ft. of existing 7 in. liner and running a new one as illustrated in Fig-1.Geomechanical Challenge and Petrophysical Demands: Due to fracturing needs, drilling toward a minimum stress direction was required even though this was not preferable from a drilling standpoint. The stuck pipe tendency becomes greater when compared with drilling toward the maximum stress direction in deep wells. Placing the well in high porosity zones required real-time geosteering using high-end logging while drilling (LWD) services in high dogleg environments. By using LWD technology with high bend rates, the required reservoir contact was achieved by drilling less footage than planned. Modified best practices played a major role in achieving these objectives.Running the Liner through the High DLS (Dogleg Severity) Environment: Drilling the short radius resulted in an averaged DLS of 30 deg/100 ft where it also reached a maximum 53 deg/100 ft across some intervals. Due to a high build rate and the azimuthal change required to reach the target. The use of oil base mud and bridging materials along with constant monitoring of mud rheology allowed the liner to be deployed successfully through high DLS section. The plan for centralizers was also modified to reduce liner stiffness while still obtaining isolation from the water bearing reservoir above the target. The success in delivering the well and returning it to production after a challenging workover job opens the door for future activity. Restoring wells by employing the short radius drilling technique provides a cost effective solution compared to conventional workover methods in many cases.

Gas migration through cement columns has been an industry challenge for many years. Formation gas/influx can migrate through the cement column resulting in gas being present at the surface. To overcome gas migration on existing wells, remedial jobs are executed, which requires detailed engineering and testing prior field deployment. The objective of this paper is to detail the effort and experimental work that took place to use different polymer resin systems in Saudi Arabia gas wells. The two polymer resin systems are differentiated by their main component, either epoxy resin or polyester resin. The epoxy resin system is prepared by mixing an epoxy resin with an aromatic amine curing agent while the polyester resin system is prepared by mixing polyester resin with norpol peroxide curing agent, filler, and silicon dioxide. This study is the first to assess the performance of two different types of polymer resin systems and evaluate their remedial operations according to the authors’ best knowledge. In addition, this paper discusses operational challenges that may occur when using each type of polymer resin system. Lab tests were conducted to measure the thickening time, the rheological properties, compressive strength, and limitations for each polymer resin system. The tests suggest that a maximum temperature of 225°F and 275°F should be maintained when using the epoxy and polyester polymer resin systems, respectively. Based on the study, the epoxy resin system is easier to control as it is composed of only two components unlike the polyester resin system, which is comprised of several components. The lab study suggests operational recommendations to increase the probability of success of the polymer resin systems.

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