This paper presents the technical advances made in the use of power swivels in replacing the rotary table. The equipment, drilling techniques and accelerated drilling time are reported. Specifically, special features of the use of a power swivel are also presented, i.e., drill up, remote pipe stabs, safety, presented, i.e., drill up, remote pipe stabs, safety, operating cost reduction, drilling down 90 ft. stands. The object of this report is to acquaint people with the recent advances in the use of the power swivel. Introduction A new electric power swivel drilling system has been developed and successfully placed in operation on two SEDCO jackup drilling rigscurrently drilling for Abu Dhabi Marine Operating Company (ADMA-OPCO). The swivel, called a Top Drive Drilling System, consists of a 1000 HP electric DC traction motor and an innovativepipe-handling system developed by Varco Oil Tools. The concept of rotating pipe directly with a motor connected to the top of the drill string, in contrast to a kelly sliding through a rotary table, is not a new one; it is commonly used on workover rigs that do not have rotary tables. A However, power swivels, as they are often called, have not been used extensively for drilling due to pipe handling compromises and the poor performance of previous designs. The Top Drive System described in this paper represents a significant step forward in the practical application of the basic concept. Its development and subsequent field use has been highly successful. Two significant improvements attributable to the new system are excellent reliability and very efficient pipe handling. Both factors are enhancing the operation of the rigs on which they are installed to a degree that both rigs have reduced overall drilling time 20%on the average well. Figure 1 illustrates the power swivel and pipe handling systems. HISTORY OF POWER SWIVELS The offshore use of power swivels and power subsstarted in the early 1950's. A Baash Rosshydraulic drive power sub unit was utilized offshore on the drill ship NOLA I. This was followed by a power swivel used on the dynamically stationed coring vessel EUREKA in the early 1960's. Several other hydraulic drive power subs and swivels were used for special applications, i.e. the GLOMAR CHALLENGER deep sea coring project. One of the first fully electric driven power swivels was a unit built and tested by ARCO for high RPM drilling tests. Brown Oil Tool and Bowen developed and marketed the first electric drive power swivels in the early 1970's.The VARCO power swivel system went into use in 1982. History has proven that a power swivel is a tool which provides good economical returns. It drills hole faster and eliminates several drill problems. The power swivel, when used in conjunction with a handling system, gives even more advantages. III SYSTEM DESCRIPTION A. Design Philosophies The factor overriding all others in the design of any power swivel is reliability. Rotary tables, kellys and kelly drive bushings have an inherent reliability as a result of many years of experience. Almost all drilling personnel are well-schooled in their use, care and maintenance. Hence, their perceived reliability is very high. On the other hand, power swivels have had only limited use. Consequently, they will not have aperceived reliability unless they can function continuously without failure and experience only minor repairs. Anything less will be interpreted by most operators as poor reliability regardless of overall performance, and most would not risk power swivel use. The power swivel's reliability can be broken down between two areas for analysis and discussion. P. 359
The western Greenland Shelf is in the early stages of exploration. There are various factors which make exploration drilling particularly difficult and shorten the operating season, i.e. ice packs, ice bergs and weather. Two summer drilling seasons, 1976 and 1977, have resulted in the drilling of five exploration wells while utilizing special dynamically stationed drilling vessels which can move in fast, position without anchors, drill and evade icebergs by fast disconnect procedures and subsea acoustic re-entries. This paper presents the pre-engineering and operating experience of two vessels used in the summer of 1977 to drill three wells within an 81 day period while dealing with the hostile, remote environment of Greenland. During the 81 day drilling period, 82 icebergs, varying in size from 8 thousand to 7.5 million tons, were sighted and tracked at locations within a 25 mile radius of the SEDCO drilling sites. INTRODUCTION The Western Greenland Shelf, where oil companies obtained leases in 1975, covers an area of 4.5 million acres. The Greenland lease area is illustrated on Figure 1 and compares in size to the oil exploration area between the Ekofisk, and Brent Fields in the North Sea. The northern and southern boundaries of the Greenland area are 68°N and 63°N, respectively. The western boundary of the lease is at a water depth of 2,000' near the middle of the Davis Stratis and within 30 miles of the Canadian border. Investigations carried out over the years by the Geological Survey of Greenland of the Cretaceous Lower Tertiary sedimentary sequence in the Diski-Nugssaq area had shown that the shales on land had a considerable content of organic material and that these shales, to a certain extent, were suitable as source rocks, mainly for gas. In addition, there are in the land area porous and permeable sandstones which could be good reservoir rocks. Combined marine and airborne investigations show that this land area constituted a local embayment separated from the extensive offshore sedimentary basin to the west and southwest in part by a Precambrian gneiss ridge, in part by an area of Tertiary basalts. It was logical to assume that sedimentary rocks of similar type and age extended below the continental shelf. In addition, it was tempting to make comparisons with the Labrador Shelf, where encouraging amounts of gas had been found in two wells drilled before 1975. Since the grant of concessions in the spring of 1975, the concessionaires have shot about 15,000 km of seismic lines. With the exception of the southern-most concession area between 63°00' and 63°30'N where the amount of seismic data available before 1975 was very little, the new seismic data have confirmed the earlier seismic mapping and provided more detail without altering the general configuration. Before 1976, the only wells drilled near the Davis Straits area were along the Canadian Labrador coast; 660 miles south; 540 miles further south along the Flemish Shelf; and 180 miles further south to Sable Island. Greenland was a vast exploration area with no subsurface drilling information.
This DaDerwas rxesented at the 18th Annual OTC in Hpuston, Texas, May 5-8, 1986. ma rna~erialis subjact to correctionby the author. permission to copy"is restricted to an abstract-of not more than 3W words. ABSTRACTThis paper presents a summary of subsea equipment analysis on the success and failures of 309 subsea Installations conducted between 1960 and 1984. The twenty-five (25) year history includes the experimental, complicated, routine, and deepwater subsea equipment installation.The summary analysis separates these into time periods and illustrates the type and percent of failures.Using the data for the period 1979 thru 1984 which represents today's technology, it is shot hat for 177 subsea installations this subsea equipment had 41 shut-in type failures or a frequency failure per well per year of 0.04. The opposite of fa%lure ia success and the analysis results for this period showed that a subsea installation can mechanically be on-line ready to produce 99.5% of the time.Operating experience from 66 subsea installations for the laat 4 years in Brazil confirms the above analysis. Brazilian data shows that for several fields produced through subsea completions, the mechanical on-line ready to produce efficiency average was 99.2 % of the available time for the year of 1984.Engineers and managers should recognize the fact that subsea completions are reliable and cost effective if the philosophy of simplicity is pursued and maintained.The use of subsea installations is projected to increase in the future. Approximately 40 subsea installations are made each year and it is estimated that this will increaae.Alternate offshore producing methods such as Floating Production Facilities will accelerate the use, reliability, and technology of subsea installations.
This paper deals with the design parameters, fabrication and sea trials of the first ship equipped for dynamic stationing having the specific requirements for drilling exploratory wells in open ocean environment.Design criteria are reviewed with regard to sea state, environment, propulsion requirements and drilling performance, including automatic control and sensing systems. Model studies and dynamic simulation analyses are presented and compared with the results of early sea trials.Operating systems are summarized, and performance expectations are related to prospective utilization of the vessel in specific ocean areas. Preliminary conclusions are given with respect to vessel response to control and propulsion parameters.
This paper presents the safety/ training conditions that exist in a decade where there are "no profit" dayrates. Safety and training programs have been condensed because of limited funds for these functions, however, the continued effort of the drilling contractor to improve safety has not decreased. For the past fifteen years, the drilling contractors have invested billions of dollars on effective training and safety programs for employees. Reduced revenues of the last 5 years have resulted in curtailment of full time safety/training personnel, however the programs that are still active afford safe operations. Safety and training continue to be a major emphasis of the oil company (Operator) and of the drilling contractor, and the contractor's field supervisors historically were trained to effectively continue safety and training programs. However, due to short term contracts and low dayrates, attrition is taking its toll. The contractor has major concerns about the people manning his operations. The experience level has dropped. The employee no longer has a feel for future employment and drugs/alcohol abuse have complicated the situation. The Operators have not changed their requirements for safety and in many cases have tied safety records with the awarding of future contracts to get an adequate effort for safety by all contractors. In the future, to insure adequate safety and training, the Operator must monetarily compensate the con-, tractor who does have good safety and training programs. The Operator company executive who today has a very profitable operation must be realistic and support the contractor on safety matters. The contractor's field supervisor must also be realistic and he must assume more responsibility to think safety and train his crews to be continually-minded of safety. Everyone must bear the cost of safety - from the corporation executives to rig crew employees. The drilling contractor is caught in the middle during this decade of hard times. The industry cannot have the Ostrich Syndrome and just want safety. The Operator must recognize that they cannot expect the contractor to spend money which he does not have available to pay the entire bill for the degree of safety which they want, which is prudent, and which is mandated by Federal and State laws. Safety programs cost money, and it will be necessary for the Operator to share in this cost. If contractor personnel know their company is being compensated for better safety, their personnel will increase interest to support safety. If the Operator gives only lip service and puts all the burden on the contractor this weakens the message to man on the rig. It has been suggested that Operator pay $200/day per day the rig is on contract. This money is paid to the contractor and is earmarked for rig safety programs. This would insure that all contractors are improving their safety programs. This incentive would be recognized by all the crew as a cooperative action of the Operator and the contractor to invest in their future. There are other incentive programs that could be sponsored by the Operator that would help the entire petroleum industry maintain the improvements made in safety and training over the past decade (Figure 1). In addition, there are specific operations that are controlled by the Operators that require improvements to help maintain the contractor safety. One example is the better packaging for handling of materials (i.e. materials from supply boat to drilling rig). The drilling contractor working with the Operators using current technology will improve safety. Fig. 1Lost-time accident frequency. Low bid should not be the only consideration for awarding drilling contracts. Safety, training and rig maintenance should be equal considerations.
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