Abstracts Conductor setting depth is critical to provide structural support for next drilling sections. The shoe strength must suffice for drilling ahead and avoid any washout and unstable zone. The objective is to design and run conductor smoothly in regards to engineering and operation aspect. Multidisciplinary approach including geotechnical, drilling engineering, and structure, was implemented during planning strategy. The pre-determined conductor setting depth was defined on the maximum mud weight to be used during drilling surface hole section in accordance to the formation strength below the conductor with the purpose of not inducing losses to the formation. Lateral distance between conductor and platform jacket pile was also analyzed to secure the jacket integrity. Anti-collision analysis was performed to prevent collision due to the existence of production well in same platform. Conductor pipe size and specification with some feature was defined to withstand under anticipated load and environment. To determine the way to achieve target depth and the suitability of hammer type, drivability analysis was performed with various anticipated condition. Considering shallow refusal depth, drill and drive was required to reduce shaft friction of soil. Another environmental challenge arise during conductor operation was unable to contain fluid and cutting returns from clean-out process causing return to cover part of the production platform facility. Some of technology were planned to mitigate this challenge. By having comprehensive conductor design, the conductor pipe in all four wells drilled has been successfully installed without any problem on platform jacket integrity and subsequent drilling section. This approach also enabled to efficiency of conductor installation where the number of clean-out and driving run could be reduced. The overflow return challenge could be fully contained by utilizing selfdesigned equipment. The overall operation days of conductor has shown improvement with 1.02 saving days on the last well which equivalent to amount of cost saving around USD 203,500.
One of the drilling challenge in Kilo Field of Offshore North West Java Indonesia is unstable hole condition. The critical formation is named Main Massive with the dominant clay-rich shale lithology. The unstable hole had caused stuck pipe, casing delays, loss of expensive tools in the hole, and undesirable sidetracks. Recently, there were 2 wells was drilled in Kilo Area. Based on the offset wells data drilled from this platform, there were some wells running in normal operation and the others were having unstable hole problems. All of the offset wells were using dispersed water based mud system in which generally, the drilling operation of those offset wells could be managed until casing run to the bottom. The recent 2 wells encountered unstable hole problem are KKNA-5 and KKNA-3ST development wells. KKNA-5 was designed to drill from the new slot using the same mud system as the offset wells from surface until intermediate section. In production section, mud system was changed to inhibited polymer referred to laboratory test result of cutting samples from surrounding area. However the unstable hole problem was still happened causing stuck pipe and BHA lost in hole. KKNA-3ST as reentry well also encountered same problem. The production section was drilled using inhibited mud system; however the unstable hole was uncontrolled while running the casing. The casing was parted and left in hole. The sidetrack drilling was decided using previous dispersed mud system, but again the casing was set shallower due to unable to run until casing point. Preliminary root-caused analysis led to the mud material quality. However, following other drilling wells in other fields was drilled without similar drilling problem in Kilo area, which mean the uncertainty or material quality was diminished. The deeper engineering analysis was also conducted without carrying out unstable hole problems. This field case study presents a new drilling challenge in Kilo Field. Further drilling study especially related to time-dependent wellbore instability shall be conducted, considering drilling operation of some offset wells was running smoothly. The integrating geomechanic study with drilling fluid design shall mitigate unstable hole problems in this area.
The Jack-up rig market is very dynamic as it is sensitive to oil prices and drilling activities. An effective strategy must be defined to achieve a successful tender process. A market survey shall be sourced from potential bidders and credible research institutions to provide competitive cost estimation and mapped available qualified rigs. Commercial structure is another factor that must be specified clearly. Numbers of wells or long term contracts will attract more rigs to enter Indonesian water that can be achieved by collaborating with other operators. It was quite challenging to establish a rig contract at first stage of tender to cover 1 (one) year duration with an unattractive owner estimation that ended up with a failed tender. By having collaboration with the host authority, other operators and potential bidders, the new strategy to have a long term contract by increasing the number of wells and contract duration to 3 (three) years can be finalized efficiently. The enhanced commercial structure consisted of rate classification as per the Indonesian Oil, Gas and Geothermal Drilling Contractors Association, modification cost, facility support service, reimbursable cost, etc. which have attracted more bidders. Finally, the jack-up rig contract can be established and agreed within the market price. The cost saving to cover future drilling projects has resulted in a total saving of USD 9.7 Million
With the far-reaching reservoir target coupled with other surface constraint including fix well slot coordinate and pre-determined conductor size, the longest well with 2.5 ERD Index in Offshore East Java was pioneered. The team has big task in hand to ensure all aspect of ERD well engineering and construction are being addressed properly within the fast-paced time frame given. One of the approaches strategized by the team is to split the high angle big hole size long interval of middle section into two casing string which was not the common architecture applied in the other offset wells. The objective was to ensure that the middle section of the well will not be compromised and avoid complication in the deeper section of the well. Worth to mention that the middle section consists combination of challenging lithology that deserve the right solution to avoid unwanted problem. There are highly kartsitified carbonate formation, shale and sand interbedded formation, and thick time dependent shale formation. To mitigate the challenges previously mentioned, intermediate section which is normally drilled and isolated with 17-1/2" hole × 13-3/8" casing in previous wells, now separated into two sections which require enlargement: 17-1/2" to 20" and 14-3/4" to 17-1/2". This paper focuses on 14-3/4" × 17-1/2" which is the most challenging underreaming operation in this well and the first of its kind in this field application. Adding to the fact that the inclination reach 75 degree in this section, SOBM and RSS BHA are deployed to mitigate the torque and drag issue. State of the art modelling tool is also used by team to define effectively match BHA and drilling parameter with minimal lateral vibration and stick slip for this section Apart from drilling stage, the enlarged hole size requires a condition to have uncommon casing size and specification, 16" intermediate semi flush liner connection and 13-3/8" full flush intermediate casing connection to ensure sufficient annular area and less restriction during running to bottom. The relentless effort to secure one the most critical ERD well construction phase has really paid off by allowing the next phase of operation to be executed as per plan thus assuring the overall well objective is met.
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