A rigorous engineering and research effort combined with targeted field testing has delivered a new generation of PDC technology. This technology is intended to be utilized for the most technically challenging drilling applications across the globe. One of the first applications identified for this new technology was at the Pinedale anticline field in Sublette County, Wyoming. At Pinedale, the operator's directionally drilled development wells target interbedded fluvial sandstones and shales of the Lance Pool (Lance and Upper Mesaverde formations). Due to surface constraints, all wells are drilled directionally from centralized surface pads. To achieve uniform subsurface well-spacing, well trajectory is S-shaped, with all directional work occurring before the pay interval is encountered at approximately 8,500 ft MD. The pay interval is then drilled vertically utilizing 6 1/2-in. PDC bits to approximately 13,400 ft MD, with the final 1,000 ft frequently drilled with diamond-impregnated bits. The sequence of interbedded fluvial sandstones and shale comprising the Lance Pool presents a difficult drilling environment. The interval is characterized by moderate but erratic unconfined compressive strengths ranging from 10 to 20 ksi exacerbated by high overburden pressures and increased hydrostatic pressures from mud weights exceeding 15 lb/gal to control pore pressure and maintain formation stability. Confining compressive strengths approaching 100 ksi (excluding formation pressures) are not uncommon. These harsh drilling conditions have led to slow penetration rates and short bit runs utilizing conventional PDC designs. The authors will describe the technologies developed and included in the new PDC bits. These new technologies have reduced the time in this interval by more than 100 hours per well, a 25% improvement over previous designs. With eight rigs running, each rig drilling one well/month, the operator is seeing productivity gains worth 308 days of drilling time over a year's time. Introduction Design principles and material technology for PDC bits has improved significantly over the last 10 years. However, the following industry challenges continue to drive the need for improved product performance:Operational costs are high as compared to historical norms.Tripping is unproductive time that increases worker exposure to potentially dangerous operations, so increased bit durability reduces both cost and exposure.Deeper more challenging wells are requiring more durable products.Steerability requirements are increasing as more challenging directional profiles are required.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe Sajaa gas/condensate field is located onshore in the Emirate of Sharjah UAE. Production is from the Thamama limestone reservoir at 11-13,000 ft. TVD. Reservoir pressure depletion is creating an ever increasing collapse pressure differential on casing opposite overlying sediments.Sajaa field has a history of collapsed casing on wells Sajaa 33 and 39, with two collapse events in the latter wellbore. The current study summarizes the theoretical effort to prevent collapse in the remaining Sajaa wells. A companion paper 1 discusses the related live well workover program.Current Sajaa completions are packerless, producing up the tubing or up the annulus between the production casing and a capillary string for corrosion inhibition. Coincidentally, the collapse resistance of the production casing is reduced by severe wear associated with the use of tungsten carbide hard banding while drilling the reservoir sections of the wellbore.Setting the context for the study, the well(s) tubular program, pore and internal pressures, and design safety factors are presented. This introductory portion also clarifies the differential collapse load to which the tubulars are subjected.Loss of collapse resistance due to severe wear is then addressed. The theory of wear prediction is reviewed, and then demonstrated, as the drilling parameters of several of the affected wells are used to predict their current state. These predictions are then compared to mechanical caliper measurements taken during intervention and repair. Further, using specially machined wear grooves, the effect of wear on collapse of a casing cross section is experimentally validated by full scale collapse tests.Results of both the wear prediction/measurement and its effect of collapse resistance are input to a probabilistic decision tree to tailor each well's workover strategy. The decision tree permits risk-weighting of alternate strategies for repairing the Sajaa casing. An important component of the decision tree is the consideration for time varying alteration of the collapse differential pressure with reservoir depletion.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe Sajaa gas/condensate field is located onshore in the Emirate of Sharjah UAE. Production is from the Thamama limestone reservoir at 11-13,000 ft. TVD. Reservoir pressure depletion is creating an ever increasing collapse pressure differential on casing opposite overlying sediments.Sajaa field has a history of collapsed casing on wells Sajaa 33 and 39, with two collapse events in the latter wellbore. The current study summarizes the theoretical effort to prevent collapse in the remaining Sajaa wells. A companion paper 1 discusses the related live well workover program.Current Sajaa completions are packerless, producing up the tubing or up the annulus between the production casing and a capillary string for corrosion inhibition. Coincidentally, the collapse resistance of the production casing is reduced by severe wear associated with the use of tungsten carbide hard banding while drilling the reservoir sections of the wellbore.Setting the context for the study, the well(s) tubular program, pore and internal pressures, and design safety factors are presented. This introductory portion also clarifies the differential collapse load to which the tubulars are subjected.Loss of collapse resistance due to severe wear is then addressed. The theory of wear prediction is reviewed, and then demonstrated, as the drilling parameters of several of the affected wells are used to predict their current state. These predictions are then compared to mechanical caliper measurements taken during intervention and repair. Further, using specially machined wear grooves, the effect of wear on collapse of a casing cross section is experimentally validated by full scale collapse tests.Results of both the wear prediction/measurement and its effect of collapse resistance are input to a probabilistic decision tree to tailor each well's workover strategy. The decision tree permits risk-weighting of alternate strategies for repairing the Sajaa casing. An important component of the decision tree is the consideration for time varying alteration of the collapse differential pressure with reservoir depletion.