This case history documents the performance of Polycrystalline Diamond Compact (PDC) bits relative to conventional roller cone and natural diamond bits in drilling a deep (14,500 ft – 18,000 ft) shale-chalk sequence in 65 wells in the Tuscaloosa Trend of South Louisiana. PDC bits were used on rotary for drilling this sequence with varying degrees of success in conjunction with four different drilling programs. Included are discussions on variables which affected the performance of the PDC bits studied. Data presented originates from company bit records and photographs compiled during normal field operations.
Summary Deposition of a cement sheath inside 9-5/8-in. intermediate casings cemented in highly deviated North Sea wells often required reaming before drilling operations could be resumed. Attempts to remove or prevent solids deposition by means of additional wiper plugs, flushes, or flow-rate variation were ineffective and led to plugs, flushes, or flow-rate variation were ineffective and led to a laboratory investigation of the factors contributing to the cement sheath formation in highly deviated wells. The laboratory study was conducted in a large-scale cement-displacement test facility previously used in similar investigations to simulate field conditions in scale-model proportions with actual field operation pumping equipment, materials, and techniques. This paper describes the identification of cement sheath deposition through case histories, test facilities, conditions, and results and indicates a satisfactory resolution for this problem. Introduction Previous studies of horizontal/deviated well cementing have focused on Previous studies of horizontal/deviated well cementing have focused on effective displacement of drilling fluid and solids from the annulus to obtain a continuous cement sheath. This study focuses on cement slurry settling within the casing string before cement slurry enters the annulus. The problems are quite similar in nature; both are characterized by loss of solids through settling from the fluid of interest during dynamic (i.e., flowing) conditions. The other investigations emphasized identification of drilling-fluid properties that control solids settling during placement/displacement. This study, however, centers on the facts placement/displacement. This study, however, centers on the facts that (1) solids are settling from the cement slurry rather than from the drilling fluid, and (2) settling is occurring in the casing string. This second point proved somewhat perplexing and was ultimately a major factor in the decision to conduct a full-scale laboratory investigation. When actions to alleviate settling were applied unsuccessfully in the field, it became apparent that the problem could be understood better by examination under controlled, laboratory-type conditions. The problem was thought to be a cement slurry or spacer-related phenomenon aggravated by the wellbore deviation angle. An examination of the cement sheath problem as identified off-shore Norway, initial attempts to alleviate the problem, and details of laboratory investigation findings illustrate the development of an effective strategy for preventing cement sheath deposition under deviated well conditions. Background Field Case Histories. In 1983, the cement sheath problem was identified on the Valhall platform offshore Norway. Well deviation angles from the Valhall platform averaged from 24 to 74; most were between 40 and 60. The first recorded cement sheath (Well A-8, Table 1) occurred at 1,900 ft and required 6.5 hours of reaming to remove. Other wells also would require reaming over the next few months, with ream times ranging from 26 to 39 hours (Wells A-9, A-10, and A-11). Initial attempts to alleviate the cement sheath problem focused on the cementing tool, which used a wiper plug design suspected of cleaning the casing inadequately, plug design suspected of cleaning the casing inadequately, Shifting to a five-wiper blade plug was no more successful at alleviating the cement sheath problem than previously used techniques, however, even when as many as five plugs were used to increase wiping within the casing (Well A-11). At this point, it became clear that mechanical remedies would not solve the cement sheath problem effectively. problem effectively. When the switch to a more durable wiper plug failed to solve the cement sheath problem, the focus was shifted to changing the cement composition. Because the cement slurry clearly did not suspend solids adequately, the fluid-loss additive was changed to increase the yield point (YP) of the slurry (Well A-12). This simple change in the cement slurry composition brought about the desired change: no cement sheath and therefore no reaming. Only one of the next eight wells cemented (Wells A-13 through A- 19) required reaming.
This work shows that rotary retort distillation is a conceptually feasible alternative for removal of oil from cuttings produced while drilling with oil base mud. The work specifically examined the response and behavior of oil base mud drilled cuttings and associated fluids to heat in a tumbling bed. These test results established the temperature requirements necessary to clean oil base mud cuttings to various cleaning limits. Heat transfer coefficients have been calculated for the test apparatus. These heat transfer coefficients have been used to establish the size of a full scale unit necessary to process 15 metric tonne/hr of drilled cuttings. The recovered products, cuttings and oil have been evaluated for toxicity. The dried cuttings were evaluated with a metal leachate test to establish extraction procedure toxicity. The distillation products were chemically analyzed and the amount of noncondensable gas was estimated.Finally a conceptual retort design is proposed for the offshore environment. Energy consumption and operating costs for a typical well are estimated.
A new wellhead installation technique has been developed and field tested. The new wellhead system employs a cold forging process which eliminates the need for welding the casing head to the initial casing string an operator sets. Advantages of the new system are its speed of installation, elimination of undesirable welding stresses, and the technique's insensitivity to weather. Described in this paper are the features of the new wellhead installation technique and details surrounding the industry's first installation on a 13-3/8" casing string in July of 1987 in the Gulf of Mexico. Also documented is a discussion of field and engineering data to test its metal to metal sealing characteristics.
A new wellhead installation technique has been developed and field tested. The new wellhead system employs a cold forging process which eliminates the need for welding the casing head to the initial casing string an operator sets. Advantages of the new system are its speed of installation, elimination of undesirable welding stresses, and the technique's insensitivity to weather. Described in this paper are the features of the new wellhead installation technique and details surrounding the industry's first installation on a 13-3/8" casing string in July of 1987 in the Gulf of Mexico. Also documented is a discussion of field and engineering data to test its metal to metal sealing characteristics.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.