Hamzah, Nurul Ezalina (Petronas Carigali Sdn Bhd) | Safiin, Norhisham (Petronas Carigali Sdn Bhd) | Abdul Rahman, Afizza Anis (Petronas) | Ibrahim, Zahidi (Petronas Carigali) | Morris, Thomas C. (Petronas Carigali Sdn Bhd) | Jenie, John R. (Schlumberger) | Chaari, Youssef (Schlumberger)
Completion operation is one of the most important contributors to successful well deliverables. Without a proper design of the accessories and efficient operation in conveying the completion assembly, the true potential of a well may not be realized. Coiled Tubing Drilling (CTD) was first attempted in Peninsular Malaysia in February 2011 and the wells were designed to be completed as Coiled Tubing (CT) re-entry sidetrack using 2-3/8?? pre-drilled liner and swell packers with maximum inclination of 90o angle and dogleg ranges between 30-60o per 100 feet.
The liner and swell packer assembly were designed to be conveyed to the target zone via coiled tubing and to go through 3 ½?? tubing with maximum clearance of 2.8?? and dual casing exit from the existing completion setup. Apart from the small and rigid clearance, another challenges that the team faced was differential sticking due to mud property that was used to maintain hole stability and to prevent the hole from collapsing before the completion was placed. Since the completion would be conveyed through high dogleg environment, the type of liner and swell packer chosen had to able to withstand the bending stresses applied to it. A small error will result in parted assembly or inability for it to be conveyed all the way to the intended zone.
This paper presents the challenges faced during the design and completion operations and discusses the program devised to overcome the above mentioned issues. Based on the lesson learnt from previous wells in which the operations were not 100% successful, the team made significant improvements in terms of mud property, swell packer design, procedure changes and introduction of friction reducer into the completion program of the final and last well of the campaign that finally enabled the liner to be conveyed to the total depth (TD) successfully.
Rahman, Afizza Anis A. (Petronas Carigali Sdn Bhd) | Hamzah, Nurul Ezalina (Petronas Carigali Sdn Bhd) | Ahmad Fauzi, Nurfaridah Bt (Petronas Carigali Sdn Bhd) | El-hariry, Haitham Fouad (Schlumberger) | Jenie, John R. (Schlumberger) | Chaari, Youssef (Schlumberger)
This paper discusses in general the phases necessary to undertake a Coiled Tubing Drilling project in a new area including: conceptual design during the feasibility study, equipment sourcing and mobilization, detailed design, operational challenges during execution, and results of the campaign. After this generic description, the operational performance will be discussed in detail.
Coiled Tubing Drilling (CTD) has been utilized on a commercial basis for many years, and can provide significant economic benefits when applied in the proper field setting. In addition to potential cost advantages, CTD can provide the following additional benefits: Safe and efficient pressure control, Faster tripping time (50+ ft/min), Smaller footprint and weight, Faster rig up/rig down, Reduced environment impact, Less personnel, and High speed telemetry. When applied to drill directional through tubing reentry wells, casing exit methods and high dogleg capability, provides the necessary flexibility to access compartmentalized bypassed pocket in the reservoir.
The drilling phase of the CTD pilot project in Malaysia started in February 2011 and was successfully completed in August 2011 with three (3) wells successfully drilled and completed in the desired target formation. The challenges faced during the beginning of the execution phase of this project were used as primary lessons learnt and contributed to a fast learning curve leading to delivering the last three (3) wells within budget.
With the successful completion of this campaign, numerous idle wells can be given a second chance to become producers again for by passed oil pockets. This is especially important for the offshore environment in Malaysia where aged platforms require a significant investment that is usually not justified for such marginal reserves. Even if sidetrack wells are planned using conventional rigs the return from such wells usually makes the cost uneconomical.
Abdul Rahman, Afizza Anis (Petronas) | Hamzah, Nurul Ezalina (Petronas Carigali Sdn Bhd) | Bin A Razak, M. Solehuddin (Petronas Carigali Sdn Bhd) | Ahmad Fauzi, Nurfaridah Bt (Petronas Carigali Sdn Bhd) | Jenie, John R. (Schlumberger) | El Hariry, Haitham (Schlumberger) | Chaari, Youssef (Schlumberger)
Peninsular Malaysia has a number of fields where reserves are not economical to be further exploited using conventional drilling methods. With the increase in oil prices over the last few decades, an operator decided to embark on a new drilling
technique of using acoiled-tubing drilling (CTD) unit to successfully access a bypassed reservoir.
One of the candidates chosen for the project was Well D in which the completion includes 3!-in. tubing in 7-in. production casing. The challenge in this well was to place the whipstock through the cased tubing before drilling operations could be performed because there was no through-tubing (3!-in.) whipstock design for 7-in. casing available on the market. The placement of the whipstock was crucial due to the existence of a shale zone uphole through which it was to be drilled thatwould createa borehole stability issue. The other reasons taken into considerations were to avoid dual-casing exit and the potential associated complications as well as to provide a uniform wellbore to create adequate annular velocity for cuttings transportation to the surface. The team proposed an atypical solution to assist whipstock setting by plugging the entire 7-in. production casing column until the end of tubingwith cement.Once the cement was hardened and tested, a directional drilling assembly with a 2.8-in. speed mill was used to mill a pilot hole through the cement plug, boring along the high side of the casing. Next, a caliper log was run on slickline to confirm hole diameter, and a whipstock wasthen runinto the pilot hole and set with it facing toward the casing. These operations were successfully performed by a rig-less CTD package.The milling assembly was run smoothly and the sidetrack window was effectively cut prior to drilling the target sand.
The successful case study presented summarizes in detail the technique used to mill such a wellbore, the challenges presented, and considerations madein designing the job, which proved to becorrect and accurate on the first attempt.
Abdul Rahman, Afizza Anis (Petronas) | Hamzah, Nurul Ezalina (Petronas Carigali Sdn Bhd) | Ahmad Fauzi, Nurfaridah Bt (Petronas Carigali Sdn Bhd) | Safiin, Norhisham (Petronas Carigali Sdn Bhd) | Khalid, Zaidan B. (Petronas Carigali) | Syaifullah, Nalom (Petronas Carigali Sdn Bhd) | Jenie, John R. (Schlumberger) | El-hariry, Haitham Fouad (Schlumberger)
The sustained and relatively high value of oil and natural gas has resulted in an unprecedented level of drilling activity and implementation of innovative methods to recover as much hydrocarbon as possible, and as quickly as possible. The resulting demand for conventional drilling rigs for programs has forced the rates high and the availability low, making use of the units difficult to justify for use in declining fields with less significant amounts of recoverable product. The by-passed reserves remaining accessible in these depleted fields exist in volumes worthy of pursuit, but must be done economically.
In many fields, operators, either intentionally or unintentionally, bypass pay zones during initial development by focusing only on the best zones. Accessing bypassed thinly laminated formations can be economically attractive but poses several challenges, especially due to aged platforms and completion string in place, also offshore environment is adding its own challenges.
Coiled Tubing Drilling (CTD) has yet to establish itself in an offshore environment. Numerous one-off projects have been tried, but commitment was never made to a number of wells to see through the learning curve and realize the potential of the application. Offshore South China Sea have a huge quantity of candidates on existing installations, installations that, due to water depths and sub sea conditions require large, expensive rigs to drill or re-enter wells. Technically the wells can be accessed with coiled tubing with drilling parameters seen regularly in other projects. The challenges for this pilot project will be equipment specification and set up, efficiently exiting the casing, and management of wellbore stability in open hole drilling and completion techniques.
The main objective of this pilot project is to bring proven technology to offshore environment to access small bypassed reserves economically and provide an alternative to conventional drilling. The well candidates were selected with strict work scope to avoid going beyond the regular CTD application to ensure learning curve and lessons learned can be implemented throughout the project and achieve the objective.
This paper will described the preparation, execution, achievement and lessons learned from this 4 wells pilot project in offshore South China Sea.
Abdul Rahman, Afizza Anis (Petronas) | Ahmad Fauzi, Nurfaridah Bt (Petronas Carigali Sdn Bhd) | Hamzah, Nurul Ezalina (Petronas Carigali Sdn Bhd) | Chaari, Youssef (Schlumberger) | Sorman, Ignatius (Schlumberger) | Jenie, John R. (Schlumberger) | Marsaleh, Zarina (Schlumberger) | Macdonald, Daren (Schlumberger)
Cementing through coiled tubing electric line (CT e-line) is not a common practice; this application is highly recommended in Coiled Tubing Drilling (CTD) applications using the existing CT e-line pipe to achieve a better time performance for sidetracking a well since using the CTD technique is mainly based on economical evaluation. Several considerations need to be taken into account while designing the job and performing the operation. The relatively high density and viscosity fluid can lead to bird nesting the cable due to high friction and excessive slack inside the pipe; it can also affect the integrity of the cable as well as the performance of the bottomhole assembly (BHA). The interface between cement and other fluids pumped through CT e-line pipe can be also affected.
A review on a feasibility study of cementing through CT e-line that was performed in 2003 in Alaska highlights all the concerns, challenges, and potential issues that can be encountered during a cementing job through CT e-line, best practices, lessons learned, and way forward to implement this technique. This review is supported by two successful case histories performed in Malaysia CTD campaign applying this technique for different objectives: remedial cementing for casing and tubing sealing in a deviated well and remedial cement plug for window recovery.
By implementing cementing through CT e-line, the effective job time was improved by avoiding swapping pipes in an offshore environment where the logistic, safety, and space accommodation is a huge challenge. The use of CTD as an economical sidetracking technology was reinforced by making the CT e-line pipe universally utilized in all the project steps, even for running and setting completion.