Structural casing jetting operations have become commonplace in deepwater environments. Having originated in the Gulf of Mexico, structural casing is now jetted in most deepwater basins in the world. Very little literature has been published regarding jetting practices. Indeed, jetting operations remain as much an art as a science to a large degree. This paper reviews current deepwater structural casing jetting job design and operational practices. Also included are several case histories of jetting failures presented in order to share learnings with the industry and to stimulate the sharing of learnings and practices. Introduction Structural casing is defined as the first string of casing installed in the well construction process. By definition, it provides structure and support for all the casing strings, the subsea christmas tree, and BOP stack. Structural casing must be able to resist bending moment loads imposed upon it by the mobile offshore drilling unit (MODU) and by future production workover operations. The casing must be installed reasonably straight/vertical, usually with less than 1° angle, to avoid drillstring wear on wellhead and blowout preventer (BOP) components. Jetting of structural casing has become the preferred method of installation in most deepwater environments where seafloor sediments allow the technique to be utilized. Operators have found the technique to be faster than the historical method of drilling a rathole and cementing the casing in place. Some deepwater basins, however, do have harder seafloor sediments, boulders, or rubble zones that prevent jetting from being an effective technique. The history of jetting can be traced back to the first floating rigs used in the U. S. Gulf of Mexico in the 1960's. Minton1 describes the installation process used to install structural casing from the first floating rigs developed by Shell Oil Co. in the early 1960's. One hundred feet of 29–1/2-in × 1.0-in wall thickness casing was set using a combined drive-jet process. The casing was connected to the drive-jet bottomhole assembly (BHA) via a J-slot tool with a 3-ft stroke to allow driving action with the BHA. The BHA consisted of 5–1/2-in drillpipe with two 22-in leaded drill collars, weighing a combined 60,000 lbm, to impart impact and add additional penetrative weight into the sediments. Figure 1 illustrates this assembly. Jetting occurred through a jet sub (no bit or motor) and returns were taken outside of the structural casing. Figure 2 depicts the process and shows both fluid and jetted solids were forced to the mudline along the outside of the casing. Minton alludes to the fact that, even from the early days of floating drilling, settling of structural pipe has been a concern. In the 1970's, development of tools such as the positive displacement mud motor and the wellhead housing running tool allowed the jetting technique to evolve2. Ports in the wellhead housing running tool allowed returns to be taken inside the casing rather than outside the casing resulting in less soil disturbance. Positive displacement mud motors allowed the rotation of bits in the jetting string and more efficient break-up and fluidization of the sediments. The jetting technique has spread to other geologic basins/geographical areas around the world. Salies, Nogueira and Evandro3 state that Petrobras began jetting of 30-in structural casing in the Campos basin in 1993. ExxonMobil Affiliates introduced the jetting concept to the west African countries of Angola, Nigeria, and Congo in the middle to late 1990's. Operators in deepwater basins off Trinidad, Canada, Australia, and southeast Asia have all adopted structural casing jetting as the preferred method of installation.

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Structural casing jetting operations have become commonplace in deepwater environments. Having originated in the Gulf of Mexico (GOM), structural casing is now jetted in most deepwater basins in the world. Very little literature has been published regarding jetting practices. The lack of published literature, combined with the complex mechanics and hydraulics of the process and the lack of detailed-soil data at most locations, results in an operation that is heavily dependent on the experience and expertise of the rigsite team. This paper reviews current deepwater structural casing jetting job design and operational practices. Also included are several case histories of jetting failures presented to share learnings with the industry and to stimulate the sharing of learnings and practices. Jetting Job Design: Casing ConsiderationsThe primary question a drilling engineer must answer is: How many joints of structural casing should be jetted to achieve sufficient load capacity? Too few joints and the casing will sink under

The Erha-7 well is a deepwater exploration well that was ultimately drilled with a dynamically-positioned rig in 1,074 m water depth within Nigeria's Offshore Mining License (OML) 133 (formerly OPL-209). During the early well planning process, the site investigation team identified numerous, extensive shallow hazards stacked in the area surrounding the Erha-7 geologic targets. These hazards were evaluated by the drill team, site investigation team, and the business unit to optimize the well location and minimize the risk of encountering shallow gas-charged sands. The final well location allowed vertical drilling of the riserless conductor-hole interval and required directional drilling below the conductor to intersect vertically stacked geologic targets. Because of the close proximity to numerous shallow hazards and the limited seismic resolution, the final well location was still deemed to possess a moderate risk of encountering gas-charged shallow sands. This paper discusses the shallow hazards planning involved with the Erha-7 deepwater well. It summarizes the limited industry experience regarding deepwater shallow gas flows and the associated safety considerations. The paper presents the modeling and evaluation of shallow gas flows and dynamic kills used to quantify the potential benefits of drilling a pilot hole, and discusses the sensitivities associated with performing an effective dynamic kill. Finally, a discussion of the dynamic kill plans developed to prevent and effectively mitigate a shallow gas flow. Introduction The Erha field was discovered in 1999 in approximately 1,074 m of water in Nigeria's Offshore Mining License (OML) 133 (formerly OPL-209). The Erha-7 well was a near-field wildcat designed to test a prospective accumulation of hydrocarbons to the north of the main field. Fig. 1 shows the location of OML-133, the Erha field, and the location of the Erha-7 well. Fig. 2 is a bathymetry map of the Erha-7 area. Fig. 3 is a seafloor rendering of the area illustrating the seafloor channel complex. The drilling rig contracted for the Erha-7 well was the fifth generation dynamically positioned drillship Deepwater Discovery. Site investigation revealed numerous, high-amplitude seismic anomalies associated with three different stratigraphic intervals and depths below the mudline (BML). The anomalies are typical of those associated with confined and unconfined deepwater channel complexes. The Erha-7 well was positioned on the proximal margin of a large, sediment filled, confined-channel complex. The channel complex consisted of multiple stacked channels that had migrated laterally through time, making it difficult to find a location within reach of the Erha-7 reservoirs that would not penetrate potentially gas-charged shallow sands. The attenuation of seismic data below high amplitudes in the confined-channel complex and limited lateral resolution further complicated the task. Fig. 4 illustrates the potential shallow hazards surrounding the Erha-7 location, and Fig. 5 shows the summary of shallow hazards prepared by the site investigation team.

SPE Members Abstract This paper presents significant environmental and regulatory initiatives developed by Exxon's New Orleans Drilling Organization. Specifically, the paper will cover drilling waste minimization techniques and disposal options, recycling of drilling waste streams, and environmentally managed drilling location design considerations. The implementation of some of these initiatives at Exxon's Chalkley field land locations have resulted in a fifty percent reduction in drilling location waste management costs. percent reduction in drilling location waste management costs. Some of these same initiatives have been successfully applied to Exxon's barge drilling locations. For operations at the environmentally sensitive Mobile Bay, Exxon contracted with a local company and assisted in the development of an economically and environmentally superior drilling waste disposal and treatment system. In summary, it is possible for drilling operators to pro-actively manage escalating environmental and regulatory challenges pro-actively manage escalating environmental and regulatory challenges through the implementation of economic and practical initiatives. Introduction The 1990's are being called the "Decade of the Environment" and the drilling industry will respond to society's increased environmental sensitivity. Responding to this heightened sensitivity while conducting drilling operations from the marshlands of Louisiana to Mobile Bay, Alabama, presents an operator with complex technical, operational, and logistical challenges. Frequently these challenges require development of unique drilling location designs and operational techniques. Exxon has developed some unique and economic drilling practices, procedures, and systems proven effective at minimizing the impact of drilling operations and proven effective at minimizing the impact of drilling operations and addressing applicable regulatory considerations. Three diverse drilling operations will be discussed. First, location design and waste handling considerations will be presented for land drilling operations conducted in Exxon's Chalkley Field in Cameron Parish, Louisiana. Included in this section will be discussions of experiences with conventional reserve pits, closed-loop mud systems (piteless drilling locations), and waste minimization techniques. Next, the application of these techniques to inland barge drilling locations will be discussed. The third section describes the development of a unique waste management system for the treatment, disposal, and potential reuse of Mobile Bay drilling mud and cutting wastes. SECTION ONE; LAND DRILLING LOCATIONS Exxon's New Orleans Drilling Organization (NODO) conducts land drilling operations predominantly in the states of Louisiana, Mississippi, and Alabama. The majority of recent land drilling activity has been conducted in south Louisiana. These are typically deep and complex wells drilled to abnormally pressured geological objectives utilizing weighted mud systems. The duration of these wells is typically between 90 and 150 days. Traditionally, these drilling operations utilized conventional reserve pits to manage drilling wastes. In this paper a conventional reserve pit will be defined as an earthen pit that receives formation cuttings, discharges from solids control equipment, location drainage, and provides a reserve of readily available fluid in the event of a well control or lost returns incident. Reserve pits also can contain discharges of mud, excess cement, and equipment wash-down water as well as completion and workover fluids. At the end of a well these reserve pits can contain upwards of 35,000 barrels of intermixed solid and liquid drilling wastes. Where permitted, the liquids are most economically disposed of by annular injection. Remaining solids are land-spread on location, buried in place, or hauled for offsite disposal. Figure 1 illustrates the layout of a typical drilling location utilizing a conventional reserve pit. P. 669