A number of papers have been presented that define the critical buckling force in inclined straight holes. This paper presents a method for calculating the critical buckling force in vertically and laterally curved and inclined boreholes. The paper includes methods for computing the bending stress of buckled pipe with tool joints. It also includes a method for computing if the deflection of the pipe at midspan will cause the pipe body to touch the wall of the hole. This approach resolves the question of how tool joints affect the critical buckling force, the curvature of the pipe, and maximum bending stresses. The paper includes plots of the critical buckling force versus hole curvature for common sizes of drillpipe and Heviwate. We also include plots of the maximum bending stress versus axial force and hole curvature for several sizes of drillpipe and Heviwate.

The number of horizontally dri 11 ed we 11 s has continued to increase in the past few years. Nearly all of these we 11 s have been camp 1 eted as "drainholes 11 with slotted or perforated liner and without a cement sheath. The majority of these have been successful in their designed intent.

Description of Proposed PaperAs the drilling industry moves towards extended-reach wells in more challenging formations, the need to identify operational solutions (e.g., drilling fluids/lubricity additives) to reduce friction, torque, and drag has become more important. Additionally, as the industry looks to maximize the use of water-based drilling fluids (to benefit from lower drilling fluid costs and improved environmental profile), the need to find novel additives that can improve lubricity has become more pressing. However, current methodologies for reducing downhole friction in horizontal wells generally involve reactive addition of lubricant products that are broadly acting, that may adversely affect the rheology of the fluid system, or that may dissipate or degrade over time. To address the need for new additives, a novel biotechnology method for encapsulating oil in polysaccharide-based polymers has been developed that selectively delivers high pressure lubricants at areas of high shear, pressure, and friction (e.g., between the drill string and formation or casing and also between drill bit and formation). ApplicationDue to the protection afforded by encapsulation, this targeted friction inhibitor can be proactively added to water-based drilling fluid systems, where it circulates through the system until conditions are met to break the capsule and release lubricant. Observations in laboratory and field testing suggest potential operational improvements in running casing, reduction of torque/drag, reduction of bit balling, and faster Rate of Penetration (ROP) from targeted lubrication. 2 SPE-169547-MS Results, Observations and ConclusionsOur characterization of encapsulated oil has shown the ability to reduce the coefficient of friction by over 80% in water-based mud formulations in the laboratory. In field-scale testing at the Catoosa Testing Facility, we have observed reductions in drag of up to 50%, reductions in torque of up to 45%, and up to 20% improvement in Rate of Penetration (ROP) in horizontal drilling after addition of encapsulated oil to a water-based polymer mud system. These results were substantially improved relative to observed results in an exploratory field well, in which ROP increased by up to 216% after addition of encapsulated oil in a saturated sodium chloride drilling fluid system. Significance of Subject MatterOur field testing and characterization in the laboratory and field have demonstrated the utility of adding encapsulated oil to a water-based mud-system to drill horizontal wells to improve the operational efficiency of drilling.

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Tests on rigs in the Gulf of Alaska show that variations in surface mud volume measurements can range from 20 to 60 bbl (3.2 to 9.5 M), depending on vessel motions. These variations were reduced to acceptable levels with conventional equipment by placing single or pairs of sensors at or straddling the centroid of the mud surfaces in each pit. Introduction Pit-volume totalizers were developed initially for Pit-volume totalizers were developed initially for conventional land rigs with steel pits. On land operations, one float or sensor is placed in each pit downstream of the constant-volume shale shaker and treating pits. The signals from each sensor are combined to provide a measurement of the total mud volume in the portion of the active system downstream of the constant-level treating pits. On most pit-volume totalizer systems, the "total volume" also pit-volume totalizer systems, the "total volume" also is displayed on a gain/loss indicator that can be set manually at the zero position. The gain/loss indicator shows the number of barrels of mud that has been gained or lost since the signal was set at the zero position. The gain/loss indicator is equipped with position. The gain/loss indicator is equipped with limit switches that sound an alarm whenever a preset gain or loss limit has been exceeded. For well control operations these limits ideally would be set at the smallest practical gain or loss. Where reasonable care is exercised in providing a constant surface-volume mud system, the gain/loss limits can be set at acceptable values. In floating drilling operations, these limits must be increased by the magnitude of any variations in the pit-volume totalizer signal due to vessel motions.This paper reports measurements of the magnitude variation in pit-volume totalizer readings that result from vessel motions if one sensor is placed in each pit and describes an arrangement of sensors that virtually eliminates the volume variations caused by vessel motions. Theory Although the mud systems on floating rigs are subject to complex combinations of heave, pitch, roll, surge, and sway, the principal effect on pitvolume totalizer measurements appears to be caused pitvolume totalizer measurements appears to be caused by the pitch or roll motions. Fig. 1 is a schematic of a pit that shows how pitch or roll motion affects the pit that shows how pitch or roll motion affects the pit-volume totalizer measurements. The variation in pit-volume totalizer measurements. The variation in pit volume measurements caused by angular motions pit volume measurements caused by angular motions between the sensor and centroid of the pit can be calculated from the following relation. (1) For the pits studied, this relationship predicts a peak-to-peak range of volume measurements of more than peak-to-peak range of volume measurements of more than 50 bbl (7.9 M) for 3 degrees of pitch and roll motions.If the single sensor is placed at the centroid of the mud-pit surface, this relationship would predict no change in volume measurements caused by pitch or roll motions. It also is apparent that the average height of two sensors placed on a line through and equidistant from the centroid of the surface will eliminate the pitch and roll motion effects. Measurements Pit-volume totalizer (PVT) measurements were Pit-volume totalizer (PVT) measurements were obtained on a floating rig during a period when pitch and roll motions ranged from 1 to 3.5 degrees. Fig. 2 is a schematic of the pits and PVT sensor arrangements studied. Tables 1 and 2 list the measurements of the PVT signal range and the pitch and roll motion PVT signal range and the pitch and roll motion measurements. Test periods generally were limited to periods of 1 hour. periods of 1 hour. JPT P. 1497