Conventional open-to-atmosphere mud returns systems present a challenge when attempting to obtain energy resources that have previously been deemed economically or technically impossible to drill due to narrow drilling windows. A narrow drilling window significantly reduces the possibility of drilling to targeted depth effectively and efficiently from cost and safety perspectives. However, it is not always the pore pressure and fracture pressure gradients that define the drilling window, as has been observed in a field in East[MA(1] Java Province, Indonesia. In this instance, the actual drilling window lay between the wellbore instability and mud losses pressure gradients. Having the bottom hole pressure lower than the wellbore instability pressure would risk collapse of the wellbore, resulting in stuck pipe, or worse, a fishing job and requirement to sidetrack the well. Thus, a steady bottom hole pressure within that window was deemed critical to successfully drill to the section target depth. The application of Managed Pressure Drilling (MPD) was selected to drill the narrow drilling window and has resulted in being able to successfully drill to the targeted depth without wellbore collapse. Data acquired from system-recorded drilling parameters enabled analysis of the wellbore condition and adjustment of parameters leading to a successful operation. Calculated friction pressure, ECD trend line, flow behavior and most importantly surface back pressure were compared as analysis subjects. The utilization of MPD equipment, including Rotating Control Device (RCD) and Automated MPD Choke Manifold, enables surface back pressure to be applied to create the required bottom hole pressure sufficient to maintain wellbore stability within the narrow drilling window. With real-time results being applied on site, as described further in this paper, drilling hazards related to wellbore instability were significantly minimized, if not completely eliminated.

One of the major problems agreed upon in CO 2 gas injection is early gas breakthrough attributed to unfavorable mobility in the reservoir. The objective of this study is to study the effect of liquid CO 2 injection to oil recovery. The core was displaced with crude oil after brine saturation. The next step was water flood by injecting 12 PV of 10,000 ppm concentration brine. Finally, the preconditioned liquid CO 2 was injected and the produced oil was recovered. The result of this study gave an interesting oil recovery with a range of 67.7 to 72.6% depending on the temperature of the CO 2 injected.

Completion phase is critical in well construction where drilling operation is achieved in static-underbalanced condition with water as circulation fluid. With utilization of Managed Pressure Drilling (MPD) equipment that consists of Rotating Control Device (RCD), Automated MPD Choke Manifold, and Downhole Isolation Valve (DIV), lower completion string can be deployed safely and efficiently. MPD technique enables safe and efficient transition after reaching target depth and prior running lower completion. The same technique allows instant and manageable bottom hole pressure upon the completion phase. This paper emphasizes the main benefits of MPD technique while running lower completion in a gas-rich well in South Sumatra. With static-underbalanced fluid presence while drilling to target depth, transition from drilling to completion phase is very crucial. The presence of DIV eliminates the needs to kill the well with heavier mud and chemical additives prior tripping out drill string to surface. DIV isolates the open-hole formation safely while drill string is pulled out and lower completion string is made up on surface. This result in easier fluid management on surface by keeping fresh water as circulation fluids, while avoids chemical settling to the pay-zone which can lead to well productivity issues. While running the completion string, prior to reaching DIV depth, RCD bearing assembly is installed to enable closed-loop and pressure-able drilling system. The DIV is then opened securely while MPD Automated Choke Manifold manages the desired bottom hole pressure by adjusting the surface back pressure accordingly. Although the fluid weight in the well is static-underbalanced, the bottom hole pressure is managed to be overbalance at all time. Lower completion string is run to bottom then its hanger and packer set subsequently to have the primary well barrier in place for further production purpose.

The South Sumatra Field in Indonesia produces from a high deliverability gas reservoir with the gas rate of each well around 50 to 200 MMSCFD. The primary target is the fractured network present in the Pre- tertiary Granite/Andesite while the secondary target is the Tertiary carbonate. In the past decade, Light Annular Mud Cap Drilling (LAMCD) is one of Manage Pressure Drilling (MPD) methods that has been frequently applied to drill in the surrounding areas of South Sumatra's oil and gas fields. The LAMCD method allows drilling to continue despite experiencing total loss of circulation in the fractured reservoir. Sacrificial fluid, usually fresh water, is injected down into the wellbore through the drill pipe. Viscous fluid with the density slightly lower than the pore pressure is injected intermittently into the annulus. The challenge occurs prior to tripping out where the well needs to be balanced. The killing operation contributes additional cost from the lost circulation materials, additional operation days or non-productive time (NPT) and inflicts damage into the reservoir due to the injected LCM. The downhole isolation valve (DIV) system is integrated into the 9-5/8″ casing string to cope with the challenge. By using this system, the requirement to kill the well while tripping out is eliminated. The successful utilization of LAMCD and DIV is elaborated in this paper as part of the drilling program and the combination of the two principles are applied. This paper focuses on the utilization of LAMCD and DIV in a case study of Drilling Well X which was drilled in the South Sumatra Field.

Recent drilling operations in Southern Sumatra area, especially Jambi and South Sumatera district, have experienced various problems upon drilling the top section, intermediate section, as well as production section. Overpressures, loss circulation and narrow window between pore and fracture gradient are common problems when drilling the top hole section. In some wells, coal caving and shale sloughing are claimed to be the reason of drilling day extension in this particular section. Overpressure zone within permeable system have cornered several field operators to activate well control system. Some field operators even had to experience blow out. The upper zone of intermediate section sometimes experience tight hole and shale sloughing, which require adequate drilling fluid management. In several wells, reactive shale is identified within the lower intermediate section, which requires the operators to utilize oil based mud to avoid clay swelling. Total loss circulation inflicted with high gas content is a normal condition when penetrating the intermediate and production section. This condition increases operational days when drilled conventionally with high potential of pipe stuck, complications in formation evaluation such as cuttings recovery and well logging, or even forcing the operators to side track the well due to sloughing. Extensive well bore clean out period also have been experienced by some operators when drilled with high barite concentration within the production zone. This paper elaborates a new drilling convention that has been practiced by the operators within these areas, evolving the commonly known Managed Pressure Drilling technique into a culture when penetrating such problems. Success stories will be highlighted when drilling through the top section, intermediate, and production section presenting risks associated from economical and operational perspective.