Drilling operation cost in development activities for oil and/or natural gas occupies large portion of the total project cost. Several approaches have been discussed for years in order to reduce the drilling operation cost. This paper represents an interactive approach towards achieving the Technical Limit for drilling operations, using an optimized philosophy characterized by sound engineering fundamental practices and their application during the planning implementation phases for drilling operations. This approach is then applied to Organizational Learning templates developed by Japan National Oil Corporation and Frontline Group, Organizational Learning Division. The fundamental premise is that all drilling operations are similar in that the irrefutable basic physical principle of force governs dynamic operations in the enchmarking processes of such as ROP, hydraulics etc. This principle is applied to METI exploratory test well “Chikappu” operation in the Heisei-12- year drilling Campaign and in a workshop conducted in Tokyo, Japan with a team of engineers comprised of Japan National Oil Corporation, and Frontline Group. The purpose of the workshop is to deliver a well construction plan, using a targeted approach beginning with the historical analysis of applicable offset information and global benchmark data, applying optimized physical principles to each dynamic operation. The assumptions are as follows, (1)The time analysis of offset information on METI exploratory test well “Tempoku” operation in the Heisei-5-year drilling Campaign results in Technical Limit Time as of 40%, Invisible Lost Time as 40%, and Non Productive Time as 20%. (2)The reality of one bit for one hole section has been achieved in each hole section, and can routinely be achieved by today's available technology. (3)Each hole section would be treated as if minimum mud weight trends were applied to optimize horsepower.
Japanese Ultra-deep Drilling and Geo-scientific Experiments (JUDGE), which aim to drill into the Philippine-Sea-Plate subduction zone from the Japanese Island, had been proposed by scientists more than ten years ago. Scientists estimate the plate can be reached with a 10-km deep borehole, and they predict that the formation temperature will increase from 200 to 400°C at that depth. Some studies were made about this project several years ago, however, no drilling proposal has been submitted to conduct this project. This paper discusses: What are the major technical issues to carry out this project? How deep can we drill into the formation with estimated formation temperature gradients?, and How should we plan this project? Numerical simulations were conducted to find out the temperature changes in the borehole during drilling operations. The results are: A 7-km hole can be drilled, but the 10km hole will be very difficult to drill with conventional drilling methods and existing muds and tools. Based on simulation results a 12-year project plan, consisting of 3-phases, was proposed. Phase-1 is 5 years and assigned to be a planning and engineering stage. A 6-km to 7-km hole was planned to determine actual formation temperature and bore hole stabilities. Based on the obtained information, necessary research will be conducted in phase-2. To test the temperature capabilities of drilling and logging tools, a 4km-deep high-temperature well will be drilled in a geothermal area. Phase-3 is the execution stage to drill the 10-km well in four years. Temperature simulation results showed that it would be very difficult to drill 10km-JUDGE well with conventional method, however new drilling methods such as casing-drilling, expandable-tube, TDS-cooling-method etc., have been developed recently. So, it seems that the JUDGE project is no longer just a scientists' dream, but could be feasible in the near future.
The 6in. hole was drilled over 660m in depth of 4, 400m in Niigata prefecture by Teikoku Oil Company. In high pressure and high temperature formation, strength of drill strings and fishing tools were considered carefully. Field investigation of DC's total revolution and magnetic particle test were carried out carefully. No DC failure was resulted due to these inspections. In some previous wells, DC failures occurred in many times. After that, magnetic particle test was decided to carry out regularly in order to prevent DC failures. No DC failures have occurred in the wells of Teikoku Oil Company after this magnetic particle test was introduced.Even though magnetic particle test was carried out by the skilled person in the first stage, currently this method is done by the drilling crews as routine work. Even though data about bit selection and bit life are not enough, results of actual experience, 50 hours bit life for tri-cone insert bit and 132m/135.5hrs bit performance for impregnated bit with down hole motor were attained. In this paper, field experience of slim hole drilling method in HPHT and several technical issues, which played the important role, are reported.
Two re-entry horizontal wells were drilled and completed by short-radius method at Khafji field in 1989, which was the first experience on horizontal drilling in Saudi Arabia and Kuwait. In 1993 horizontal drilling activities were initiated by medium-radius method, and 31 new horizontal wells and 15 re-entry horizontal wells, including the above-mentioned two wells, were drilled and completed so far. In 1991 and 1992, “A Study of Completion of Lateral Holes” and “Rock Mechanics Study” were conducted to establish company's policy and to highlight formation damage control, wellbore stability analysis and drilling fluid properties, respectively. In 1997, “Engineering Study for Horizontal Drilling and Completion” was conducted to review the horizontal drilling performance from 1994 to 1996. In 2000, another review was conducted to further reduce the days and cost. At the beginning of the horizontal drilling activities, a new horizontal well was planned with 70 to 80 days and US 5 to 6 million and a re-entry horizontal well was planned with 45 days and US 3.2 million. Through the many field experiences and studies, the performances and costs of the horizontal wells were reviewed and improved. At the moment, a new horizontal well is planned with 40 to 50 days and US 3.5 million and a re-entry horizontal well is planned with 30 days and US 2.1 million. Our ambitious, aggressive and ultimate target is 25 to 30 days and US 2.5 to 3 million for a new horizontal well and 20 days and US 1.7 million for a re-entry horizontal well.
JAPEX as an operator accomplished deepwater drilling of two exploration wells in 800m of water in the Indonesian sector of Timor Sea at the period of 1999 to 2000, under an unstable political situation after the Suharto era in Indonesia and under the influence of struggle for independence in East Timor. The best possible planning and preparation of drilling operation support as well as the most suitable selection of drilling rig and marine fleet were key issues to success under such circumstances for the subsequent drilling operations at the minimum drilling cost, coming out approximate 60% of the originally estimated cost. One particular issue to be focused on in this paper is the logistics support for safe and cost-effective operation, with an application of a fit-for-purpose warehouse vessel mooring in deepwater near the drilling rig with most drilling tools and materials necessary for two wells in a remote area, over 2, 000km away from main supporting bases of oil industry. JAPEX planned it well and did it well at minimum cost as an operator among the major oil companies as partners.
Japan Drilling Co., Ltd (JDC) has been carrying out drilling operations under a footage contract in Persian Gulf since December 1999 utilizing a jack-up rig Hakuryu-8. The footage contract is one of the incentive contracts, which is named from a rate is defined by price per foot. The footage contract is a very common contracting style in US land rig operations, while it is not so common in offshore operations, especially in Asia. This report intends to serve as an induction to the footage contract, JDC's approach to the contract, and a result of the first year operations performed by JDC to verify that this type of contact is beneficial for both operators and contractors. The footage contract shifts risks of hole trouble and equipment trouble onto a contractor in footage section; however, the contractor would benefit more from effective and faster operations with less non-productive time. An operator would benefit from the best possible performance by the contractor, hedging the risk of hole trouble to the contractor and completing a well with shorter time. As a result of five wells drilled in year 2000 by JDC, the operator saved 39 days of operating days and 17 percent of operating costs. And those performances were highly appreciated by the operator.
A deep well multi stage fracturing project is under going the Minami Nagaoka gas field. Permeability of the target formation is 10-2md order of tight volcanic rocks, deposited deeper than 4, 000m, which creates a high temperature, and high pressure circumstance. In addition, rock facies changes almost foot by foot, and some regions are highly naturally fractured. These characteristics make it difficult to have successful frac operation by a classical approach. Recent study and feed back from the two premature screen out experiences in the Minami Nagaoka gas field suggested that near wellbore tortuosity, which caused multiple fractures to grow, was estimated to be higher than anticipated. In this condition, the net fracturing pressure became increasing due to individual fracture push each other with the fracture width keeping narrow. Increasing net pressure led to the high surface treating pressure, the injection rate would be limited, finally ended in premature screen out. To eliminate this phenomenon, the newly drilled well last year was designed for the high-pressure fracture treatment. Several new design concepts such as extremely overbalanced perforation (EOB), step down test, and proppant slug techniques are planned to observe the degree of near wellbore tortuosity and will be tried to reduce these tortuous paths.
In the design of deviated well trajectories, the minimization of torque and drag has conventionally been one of the most important factors to be considered. Once the well starts production, however, thetrajectories of the deviated wells become strongly influential on the vertical pressure loss performance intubings. Well trajectories, therefore, need to be well-optimized using production engineering-basedevaluations for minimizing the pressure loss in the vertical flow in tubings and hence for maximizing the production rate from the reservoir. In this paper, well trajectories and tubing parameters of deviated wells were optimized in terms of profit-based objective functions. The net present values from the well production operations, after discounting the well drilling costs, were defined as the objective function for optimization. In the optimization process, Newton-type methods, the polytope method and Genetic Algorithms were applied and their efficiency and stability in optimization calculations were investigated. Among the optimization calculations, Newton-type methods showed poor optimization performance due to the lack of robustness to avoid the convergence to local maximum/minimum on the objective function surfaces. Genetic Algorithms showed the best performance in finding optimum well trajectory and tubing parameters. In some cases, the polytope method performed well, though the performances of the polytope method were dependent on initial guess values for the iteration. With the appropriate application of production optimization methods in deviated well designs, more profitable and realistic well design would be enabled for the future reservoir development.
Heterogeneity observed in Minami-Nagaoka gas field is attributed to the presence of discrete rock bodies with a limited extent andimpermeable edges. Obtaining relevant parameters through comprehensive well-test analyses enables us to generate stochastic realizations of discrete rock bodies. For the entire reservoir, however, 40 million cells are required to honor individual geometries, which is too many to be used in flow simulation. To overcome such difficulties, scaleup techniques are often adopted to coarsen detailed systems to scales appropriate for flow simulation. There arises a problem of how to compute effective permeability (keff) at larger scales on the basis of the geological model. Of interest in this paper are to establish a methodology for computing keff appropriate to the reservoir containing discrete rock bodies and to develop keff correlation by conducting sensitivity studies. The resultant correlation equation is verified against naive permeability distributions and its utility is demonstrated through history matching procedures for the actual pressure data from Minami-Nagaoka gas field.