fax 01-972-952-9435. AbstractHigh angle wells drilled into finely laminated shale are often found to be less stable than comparable wells drilled into nonlaminated rock. This can be attributed to a variety of factors including, but not limited to, well trajectory, the in-situ stress field, rock strength anisotropy, shale reactivity issues, chemical imbalances between the drilling fluid and shale pore fluid, and many others. However, due to the lack of available data some of these mechanisms are difficult to quantify and therefore are typically not accounted for during well planning. This can result in significant wellbore instability issues that substantially elevate drilling operation costs.In this paper, a comprehensive approach to account for many of these wellbore instability mechanisms is outlined. A plane-of-weakness model is utilized to account for the effects of weak bedding planes and other discontinuities. The model uses parameters that are obtained by curve fitting triaxial strength test results conducted at various angles with respect to bedding. Additionally, traditional mechanical and chemical effects were also addressed and incorporated into the pre-drill model to assist in well planning. The model was then implemented at the Terra Nova field for the case of a highly deviated wellbore drilled through finely laminated shale nearly parallel to bedding.Real-time monitoring of measurement and logging while drilling data was key to identifying the unstable sections so that the root cause of instability could be diagnosed. The appropriate remedial action was then applied and wellbore instability problems were mitigated.Both mechanical and chemical borehole instability models were applied in a case history to evaluate the potential for wellbore instability. In particular, bedding-plane related and chemically-induced instability were addressed and overcome through comprehensive modeling and the deployment of modified operational procedures.

High angle wells drilled into finely laminated shale are often found to be less stable than comparable wells drilled into non-laminated rock. This can be attributed to a variety of factors including, but not limited to, well trajectory, the in-situ stress field, rock strength anisotropy, shale reactivity issues, chemical imbalances between the drilling fluid and shale pore fluid, and many others. However, due to the lack of available data some of these mechanisms are difficult to quantify and therefore are typically not accounted for during well planning. This can result in significant wellbore instability issues that substantially elevate drilling operation costs. In this paper, a comprehensive approach to account for many of these wellbore instability mechanisms is outlined. A plane-of-weakness model is utilized to account for the effects of weak bedding planes and other discontinuities. The model uses parameters that are obtained by curve fitting triaxial strength test results conducted at various angles with respect to bedding. Additionally, traditional mechanical and chemical effects were also addressed and incorporated into the pre-drill model to assist in well planning. The model was then implemented at the Terra Nova field for the case of a highly deviated wellbore drilled through finely laminated shale nearly parallel to bedding. Real-time monitoring of measurement and logging while drilling data was key to identifying the unstable sections so that the root cause of instability could be diagnosed. The appropriate remedial action was then applied and wellbore instability problems were mitigated. Both mechanical and chemical borehole instability models were applied in a case history to evaluate the potential for wellbore instability. In particular, bedding-plane related and chemically-induced instability were addressed and overcome through comprehensive modeling and the deployment of modified operational procedures. Introduction Wellbore instabilities have plagued the drilling community within the petroleum industry for many years. Despite the development of sophisticated borehole stability models designed to mitigate wellbore instabilities, the amount of wellbore instability-related incidences still exceed 40% of drilling non-productive time (NPT) and account for nearly 25% of all drilling costs1. These result in estimated annual wellbore stability-related expenditures in the order of billions of dollars worldwide. This sort of NPT can seriously jeopardize project economics and therefore it is of critical importance to reduce instances of wellbore instability. In this paper, we will first outline some wellbore instability mechanisms that need to be considered when drilling high angle wells. The intent is to accentuate some of the borehole failure mechanisms relevant to extended reach drilling (ERD) wells. Additionally, a modified anisotropic strength model is used in a successful case study highlighting drilling experiences of several high angle ERD wells from the Terra Nova field. Wellbore Instability Mechanisms in High Angle Wells It is well known that instances of wellbore instability increase in high angle wells2–6. This is usually attributed to mechanical failure of the rock due to unfavorable orientation of the wellbore with respect to the in-situ stress field. The result is a significant reduction in the safe mud weight window leading to premature shear and/or tensile failure. These types of failure mechanisms have been well documented in the literature and will not be discussed again here.

Improper planning and execution of deepwater drilling programs can lead to high costs and unsafe conditions. Proper well planning requires reliable estimates of the expected pore fluid pressure and formation strength prior to drilling. Such pressure predictions are based on integrated seismic and offset well data. A new, rock model-based approach especially suited for deepwater pore pressure imaging is introduced here and applied in an example of a deepwater Gulf of Mexico well. P- and S- velocities were determined both at an offset well and for the future drilling location, using prestack seismic full waveform inversion. Both predicted velocities were later verified with log measurements. Using the new model, a significant pore pressure increase at depth was predicted before drilling the well and verified while drilling (Figure 1). For the entire well, the predicted and measured pore pressure gradients agree within half a pound per gallon equivalent mudweight (Figure 1). The shear velocity, and the extracted shear modulus, proved to be excellent indicators of low effective stresses, corresponding to overpressured formations (Figure 2). Introduction It has been common practice to predict pore pressure before drilling from conventional seismic stacking velocities with a normal compaction trend analysis using, for example, the well-known Eaton approach (Eaton, 1972). Velocities that appear to be slower than the ‘normal velocities’ are indicative of overpressure, which then is quantified using an empirical equation. However, there are several problems with this approach. First, conventional seismic stacking velocities are usually unsuitable for pressure prediction since they are not "rock or propagation velocities" (Al-Chalabi, 1994). Second, these velocities lack resolution in depth. Third, in a deepwater environment, sediment loading often has been so fast that pressures in these sediments are above hydrostatic (geopressured) right below the mud line - unlike, for example, on the continental shelf of the Gulf of Mexico (Dutta, 1997). This prevents development of a normal compaction trend, thus invalidating the entire approach in the deepwater. Our new approach is trendline independent and uses a deepwater rock model for geopressure analysis. The model (or approach) is based on several seismic attributes, such as velocities and amplitudes and is calibrated with offset well information. Pore pressure is calculated as the difference between overburden stress and effective stress. The effective stress affects the grain-to-grain contacts of clastic, sedimentary rock, and consequently, the velocities of seismic waves propagating through such rock (Domenico, 1984; Dutta, 1997). The rock model has various components: relations between porosity, lithology and velocity, clay dehydration, and transformations relating both density and Poisson's ratios of the sediments to effective stresses acting on the matrix framework. The key inputs that drive the rock model are velocities (P and S) obtained from a variety of velocity tools. Iterative velocity calibration and interpretation are two essential steps in the prediction process to ensure that the velocity fields are within the realm of expected rock or propagation velocities. In the following study, we demonstrate how the P- and S- velocities used in a Gulf of Mexico example were derived using prestack waveform inversion and we describe the rock model in more detail.

Lafayette. Magana's research interests are centered on the integration of cyberinfrastructure, computation, and computational tools and methods to: (a) leverage the understanding of complex phenomena in science and engineering and (b) support scientific inquiry learning and innovation. Specific efforts focus on studying cyberinfrastructure affordances and identifying how to incorporate advances from the learning sciences into authoring curriculum, assessment, and learning materials to appropriately support learning processes.

We hypothesized that a solar-powered system designed to cool heat-stressed sows would improve sow performance and reduce use of fossil fuels in farrowing rooms. To test this hypothesis, we used two mirror-image, farrowing rooms equipped with 16 farrowing stalls each. Each farrowing stall in the COOLED room was equipped with a cooled flooring insert (Nooyen Manufacturing) under the sow and a single nipple drinker delivering chilled drinking water. Circulating water cooled by a water-source heat pump that was powered by a 20 kW photovoltaic solar array cooled the floor inserts (15 to 18°C) and chilled the drinking water (13 to 15°C). Heat harvested from sows partially warmed water (43 to 48°C) that circulated through pads in the piglet creep area. The CONTROL room was nearly identical to the COOLED room except there was no cooling and supplemental heat for piglets was provided by one heat lamp (125 W) per farrowing stall or an electric heating pad (Innovative Heating Technologies). Three farrowing groups were studied during summer and room heaters kept rooms above 24°C to ensure sows were heat stressed. Electric consumption in COOLED and CONTROL rooms was measured. Data were analyzed using Proc Glimmix with room treatment as a fixed effect and farrowing group as a random effect. The cooling system reduced sow respiration rate and body temperature (Table 1) which increased feed intake and reduced weight loss of sows over the 21-day lactation. However, the cooling system did not increase litter size or weight at weaning. Electricity use in the CONTROL room (26.4 kWh/d) was lower (P< 0.01) than the COOLED room (79.6 kWh/d). The solar array produced 91 kWh/d on average. In conclusion, the cooling system studied partially mitigated heat stress of lactating sows but did not improve sow performance and did not noticeably reduce consumption of fossil fuels.