Chevron Thailand, on average, drills 12000' MD / 8200' TVD wells in about 4.5 days. The factor that most contributes to this level of performance is the "offlining" of as many drilling rig activities as possible. In our drilling operation almost all pipe handling and cementing operations are performed offline (i.e., off the critical operations path and therefore simultaneous to other activities on the rig). We have now taken the next logical step in performing offline operations. In May 2007, Chevron Thailand introduced the world's first simultaneous open hole wireline logging and drilling operation on Seadrill RT-7 (a tender-assist drilling rig), and presently is deploying the same system on additional tender-assist and jack-up rigs. This paper describes the concept of offline open hole wireline logging and the engineering design of the components that make this new concept an operational reality. The paper also discusses the engineering required to integrate the unique offline open hole logging components with existing rig systems (for both tender-assist and jack-up rigs). This complex integration of newly designed components with existing rig systems is the path by which Chevron Thailand is setting a new performance standard in offshore drilling. The benefits of this new system have proven to be significant in improving Chevron Thailand's already world class drilling performance. Introduction Recent increases in offshore drilling rig spreadrates coupled with global shortages in newly available rigs have forced all exploration and production companies to realize that increasing the efficiency of their existing rig fleet may be the last avenue by which they can attempt to get more wells drilled and simultaneously reduce their cost per well. This realization is what drove Chevron Thailand to develop a process for performing open hole wireline logging off the critical path of a drilling operation. Under-rig-floor (URF) open hole logging is, as the name connotes, a technique that allows all open hole logging operations to be performed underneath the rig floor instead of on the rig floor. This, in turn, leaves the rig and rig floor personnel unimpeded to do what they do best - that is, drill. Figure 1 shows a basic schematic of one type of URF open hole logging configuration. By making the single, but complex, change of performing all logging operations underneath the floor of the rig, Chevron Thailand is on its way to drilling wells 10% faster (and cheaper) than before. From the outset, it should first be conceded that logging open holes using "logging while drilling" (LWD) technology is an acceptable alternative to the ideas presented in this paper. However, when either option can be exercised without impacting critical path operations on a rig, the wireline-conveyed logging option is certainly the less expensive, and therefore preferred, option. Furthermore, the extreme formation temperatures encountered in the Gulf of Thailand (around 400°F) make wireline open hole logging the preferred option, whenever hole geometry permits, because of the more robust nature of wireline tools. As mentioned above, the ultimate economic benefit of this technology is a 10% reduction in time and cost for drilling an average Gulf of Thailand well. Considering that Chevron Thailand drills 300–400 wells per year (of which at least half are candidates for this logging technique), it is easy to see that the total benefit to the Thailand business unit is substantial. Because of the small, compartmentalized nature of Gulf of Thailand reservoirs, much of Chevron Thailand's success or failure hinges upon being able to drill as many wells as possible, as cheaply as possible. The technology presented in this paper accomplishes both.

Originally discovered in 1993, the Stag oil field, on the North West Shelf of Western Australia, has proven to be both a prolific and complicated reservoir since production began in 1998. To date, more than 56 million barrels have been produced, in addition to significant volumes of water and glauconite, which has resulted in complex changes to the reservoir over time as the field has produced. Because the reservoir is shallow, at 680 m true vertical depth subsea (TVDSS) with shallow carbonates causing noise issues and imaging challenges, Stag Field remained largely invisible on seismic data. To address these issues, a 220-[Formula: see text] 4C-3D ocean-bottom cable survey (OBC) was acquired in early 2008. Subsequent processing and interpretation of these data, including a joint multicomponent inversion, have resulted in drilling six successful new wells with additional wells currently underway and planned in the near future.

Summary Originally discovered in 1993, the Stag oil field, located on the Northwest shelf of Western Australia, has produced more than 58 million bbl since production began in 1998 (Goodacre et al. 2000). The field is shallow (680 m subsea), encompassing highly unconsolidated and highly permeable sandstone. Reservoir depletion, unconsolidated rock, water breakthrough, and sand production have created conditions under which infill-drilling campaigns have become increasingly problematic in the Stag field in recent years. There have been numerous papers documenting the history of the Stag field (McDiarmid et al. 2001; Muecke et al. 2002; Wibawa et al. 2008). On three recent infill wells, the intermediate 12¼-in. intervals were drilled and cased with casing-while-drilling (CWD) technology with a rotary-steerable system (RSS). This was used to navigate wellbore congestion, to drill designer well paths to avoid "incoherencies" [a seismic attribute that is mappable and correlates with drilling problems (Chima et al. 2012)], to land the horizontal section, and then to drill horizontal tangent sections out to the initial reservoir penetration (liner point). The CWD applications progressed from a "new technology" trial to a stretch reach and performance goal, to finally successfully being used as a key enabling technology to drill a well that might otherwise be undrillable because of instability issues. The directional CWD 12¼-in.-hole intervals were drilled from just below the 13-⅜in. surface casing to the 9⅝-in.-casing point, building from 25° inclination to horizontal and holding thereafter. This program (the first applications of this type in Australia) resulted in two consecutive world-record runs. The result is that CWD is a viable enabling technology that will be used to drill future Stag infill wells and should be considered as a viable alternative on other drilling projects. This paper will discuss the identification of the technology application, planning, implementation, results, and lessons learned. This paper will end with a notional conversation regarding CWD becoming a mainstream method.

Originally discovered in 1993, the Stag Oil Field, located on the Northwest Shelf of Western Australia, has produced over 58 MMbbls since production began in 19987. The Field is a shallow (680m SS), highly unconsolidated, highly permeable sandstone. Reservoir depletion, unconsolidated rock, water breakthrough and sand production have created conditions where infill drilling campaigns have become increasingly problematic in the Stag field in recent years. Numerous papers have documented the history of the Stag Field's colorful past12-13, 23. On three recent infill wells the intermediate 12 ¼?? intervals were drilled and cased using Casing while Drilling (CwD) technology using a rotary steerable system. This was used to navigate wellbore congestion, drill designer wellpaths to avoid "incoherencies?? (a seismic attribute that is mappable and correlates with drilling problems5), land the horizontal section and then drill horizontal tangent sections out to the initial reservoir penetration (liner point). The CwD applications progressed from a "new technology?? trial to a stretch reach and performance goal, to finally successfully being used a key enabling technology to drill a well that might otherwise be undrillable due to instability issues. The directional CwD 12 ¼?? hole intervals were drilled from just below the 13 3/8?? surface casing to the 9 5/8?? casing point, building from 25 degrees inclination to horizontal and holding thereafter. This program (the first applications of this type in Australia) resulted in two consecutive world record runs. The result is that CwD is a viable enabling technology that will be used to drill future Stag infill and should be considered as a viable alternative on other drilling projects. This paper will discuss the identification of the technology application, planning, implementation, results and lessons learned. This paper will end with a notional conversation regarding CwD becoming a mainstream method.

The Benchamas Development in the Gulf of Thailand is an oil play in a predominantly gas-condensate region. This development is unique in that the operator has significant oil reserves of high pour-point crude in several zones. Some zones have gas caps; others don't. Column heights are variable. The project is being developed as a waterflood with horizontal and monobore producers and injectors. The initial phase of horizontal producers were completed with sand exclusion capability, consisting of multilayerd sintered screens. This has so far proved to be effective. The Benchamas Waterflood project is comprised of eight stacked, compartmentalized, sandstone reservoirs. These sandstones are fluvial channels and are discontinuous. The waterflood is designed to maintain oil viscosity and gas cap location to maximize recovery. The economic impact of this waterflood is estimated to increase the recovery from an estimated 12–18% (primary) to 25–35% (secondary) of the OOIP. During the design stage of the waterflood project, simulation indicated that some horizontal injector wells would be required to enable the required injection rates. Three horizontal injectors were therefore planned. The drilling, completion, and clean up of these wells presented the Benchamas Asset Team with a series of unique challenges. Rock mechanics analysis was conducted in the decision process to address the need or lack of need for sand control. Results will be discussed. Drilling fluid and flow back aspects of the wells were carefully examined in order to avoid some of the problems of horizontal injectors drilled in other parts of the world by the company. An extensive literature search revealed that the laboratory work required to adequately address the issues comprehensively had not been done. The company and the fluids vendor collaborated to conduct the laboratory tests that were required to determine the correct combination of fluids and clean up procedures necessary to successfully install these wells. This paper will highlight the unique design challenges presented to the Asset Team, discuss the efforts that were undertaken to address these challenges and the results, and present the field results of the drilling, completion, clean up, and final injection results. Introduction The Benchamas Field is one of several fields located in the B8/32 Concession in the Gulf of Thailand. The concession is located some 180 kilometers to the South of Rayong and some 80 kilometers east of Koh Samui (figure 1). The Benchamas Field was discovered in 1995 by the concession partnership with the Benchamas 1 well. The Benchamas Production License Agreement was issued in June 1997. The Benchamas field covers 411 sq. km. and operates with 3 wellhead platforms, a processing platform, a quarters platform, and an FSO (figures 2&3). Production was initiated in June 1999. Production capacity was 25000 bbls per day oil and 180 MMSCF per day sales gas. Capacity has been increased to 40,000 bbls per day. Plans are underway to increase liquid production capacity to 75000 bbls per day. The field is uncharacteristic in the Gulf of Thailand in that it has several sizable oil zones in this predominately gas region. The Oil Reservoirs are in the BWA and BWB platform areas. The third and southernmost platfrom, BWC, is primarily gas and condensate. The field consists of multiple stacked zones of Miocene age sediments. The depositional environment is fluvial braided river channels. The depositional environment has resulted in a very heterogeneous set of reservoir packages.