The Serang Field, offshore East Kalimantan, Indonesia was discovered in 1973. Production started in 1993. Although it is a mature field with 120 wells, drilling still faces challenges in the form of severe lost circulation and stuck pipe events. Side tracks often need to be drilled and drilling budget overruns can be significant. The 2006 drilling campaign of 5 wells saw the loss of several BHAs and needed 4 sidetracks, due to stuck pipe events. In order to improve the drilling operation and to uncover root causes of the losses and pack-offs, a detailed geomechanical evaluation was conducted. The study began with a comprehensive data audit and drilling event review. All the captured information and log data was then used to create a Mechanical Earth Model (MEM) for wellbore stability planning of future wells. Key findings of the study were that lost circulation occurred in high permeability zones in shallow carbonates (8-1/2" intermediate hole section) and were not caused by drilling induced fractures. A contingency plan was developed to drill to section TD with sea water, should losses occur. Breakouts, aggravated by low mud weights, lost circulation events, high deviation and slim hole contributed to poor hole cleaning, which caused the packoff incidents in the 6 1/8" sections. Safe and stable mud weight windows were established to mitigate hole collapse and stuck pipe. Since losses can occur even at low mud weights but do not usually have severe consequences, the team decided it was more important to focus on avoiding breakouts and improve hole cleaning with higher mud weights, improved drilling fluids with stress cage system to drill through depleted reservoirs, controlled drilling, ECD management to prevent formation breakdown and the use of Rotary Steerables to improve hole cleaning. The recommendations of the study were incorporated during a 3 well drilling campaign in 2009. All 3 wells were drilled and completed within budget and without stuck pipe incidents.
Along with the aging equipment and facilities, offshore platforms especially topside facilities, encounter increasing challenges in maintaining asset integrity and reliability. Aging factors such as corrosion mainly needed maintenance and repair. The scope of the maintenance and repair varies from minor-major level repair, difficulties, and resources of the work. An assessment of every asset deterioration is required to develop a scope of work, method, resource, and schedule. This paper describes an optimization model that can be used to plan a repair campaign based on the variety of the repair by finding a categorized and assessed the detail of the asset deterioration. The methodology of the optimization starts from listing all corrosion deterioration in the topside facilities, complete with detail of categories contains deterioration types, location, risk, difficulties, etc. The optimization model functionality is demonstrated in several cases, generated from actual deterioration data. A formula of the model is created to spread deterioration type for a selected specific methods of repair, including detail related to repair method, schedule, resources, including expected result. All repair action data will be collected and allocated into a campaign sequence. The result shows that significant resource savings can be made by adapting the optimal solutions from this model compared to an unplanned corrosion repair campaign. This model also covers asset repair that cannot be executed by the general maintenance team in a large scale repair campaign. The other benefit is to address the applicability of each repair method to minimize time-consuming repair campaign and shutdown time. The benefits of this paper are as a reference of the optimization model for the planning of a repair campaign, especially for facilities with significant amount of topside asset deterioration. Previously the repair campaign is not planned, produces further asset deterioration and increasing the risk of the topside facility for the offshore platform.
The requirement of drilling in very close proximity to adjacent wells in surface hole section has been common as field become more crowded. This is true especially in offshore mature field where the last wells are drilled on a dense platform. In Santan Field, East Kalimantan, conductor pipes were driven between the existing wells since sidetrack or platform extension options were not available at the time while there are still opportunity for infill and step out wells. This situation introduces challenges on well construction in term of collision avoidance since the spacing between the wells are tight from surface point. The distance between slots is as low 1 meter from center-to-center, and 0.64 meter between wall-to-wall. Directional works was also required at shallow depth to kick of the well as per trajectory requirement. The risk of unplanned intersections with adjacent well can lead to financial loss, personnel safety as well as environmental issue. A comprehensive risk assessment were conducted during the planning phase as the safety of drilling operation has been one of the main concerns. Mitigations plan were then formulated with the objectives to manage the negative consequences to acceptable level. During the planning phase, detail anti-collision procedure was executed to evaluate the collision risk. On the field, several activities were carried out on adjacent wells prior to rig move in as mitigations measure: 1) Rig less resurvey, 2) Well integrity inspection, and 3) Well barrier placement. While drilling, following strategies were performed: 1) GWD utilization, 2) Monitoring on subject and adjacent wells, and 3) Collision-tolerant drilling bit application The all-surface hole were drilled safely without any HSE or reliability issue. No major indications of well collision were observed. However, the drilling time took bit longer than usual performance due to drilling controlled manner for anti-collision precautions. This paper explain how well collision mitigations was implemented in Santan Field, East Kalimantan, which can be a reference for further drilling as a successful case of top-hole drilling on a dense fixed platform. The method is expected to gain economic value, which is notably beneficial in mature field.
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