Optimal Azimuth Research Articles

A bump on the upper surface of the Philippine Sea plate beneath the Boso Peninsula, Japan inferred from seismic reflection surveys: A possible asperity of the 1703 Genroku earthquake

To reveal a subsurface structure beneath the southern part of the Boso Peninsula, Japan, where the Philippine Sea plate is subducting and great interplate earthquakes associated with the subduction occur repeatedly, we conducted a new seismic reflection survey from March to April 2005 (Boso05). We also reanalyzed old multi-channel seismic (MCS) survey data that had been collected off the Boso Peninsula in 1978 (SK78). We found clear strong reflectors beneath the southern coast of the Boso Peninsula. Since common mid points (CMPs) were distributed widely beneath the study area owing to the design of the receiver and shot lines of Boso05, we selected appropriate directions of stacking lines to get the best image of the dipping reflectors by optimum azimuth search (OAS) processing. We carefully checked the seismic profiles at the intersections of the survey lines to confirm the NNE-dipping configuration of the strong reflectors. These strong reflectors were interpreted as the upper surface of the subducting PHS plate from their locations and the estimated velocities beneath the reflectors. Furthermore, these reflectors revealed a topographic high (bump) beneath the southern coast of the Boso Peninsula where the source fault of the Genroku earthquake of 1703 is thought to be located.

Geomechanics Optimizes Field-Development Strategy of Deep Gas Reservoir

This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 108891, "Using Geomechanics To Optimize Field-Development Strategy of Deep Gas Reservoir in Saudi Arabia," by Mahbub S. Ahmed, SPE, Saudi Aramco; Thomas Finkbeiner, SPE, GeoMechanics International; and Adnan A. Kannan, SPE, Saudi Aramco, prepared for the 2007 SPE Asia Pacific Oil & Gas Conference and Exhibition, Jakarta, 30 October-1 November. The paper has not been peer reviewed. Saudi Aramco has embarked on drilling long horizontal and maximum-reservoir-contact wells in deep gas reservoirs. The regional stress is important in predicting wellbore stability and production performance. A detailed geomechanics study was made, and its results were incorporated into the decision tree. The objectives were to find the optimum azimuth to place horizontal wells that would minimize the risk of hole breakouts, optimize drilling-mud weights, and ensure sustainable production under depletion mode. Introduction The subject field is a north/south-trending anticline. The target reservoir is the Permian Unayzah formation, which was discovered in 2000. The reservoir has three geological units: Unayzah-A, siltstone, and Unayzah-B. Because of stratigraphic considerations and constraints on wellhead placement on the surface, field development with highly deviated horizontal drilling is required to reach the target reservoirs. Reservoir management decided to extend the horizontal wells as far as possible to maximize reservoir contact and, hence, production from the Unayzah formation. Because of the highly deviated/horizontal nature of the planned development wells, it was decided to gain a better understanding of whether geomechanical processes might be of concern to wellbore stability. If so, could well integrity be maximized by use of correct mud weights and well directions that would ensure stable conditions during drilling and production? Determining Stress Orientation Approximately 2,500 ft of electrical wellbore-image data covering the Unayzah-A, -B, and parts of Unayzah-C reservoirs from the first four vertical wells drilled in this field were analyzed. The image data were calibrated, verified, and dynamically normalized to provide optimal image quality. Overall image-data quality in all four wells was fair to good. This analysis identified and characterized stress-induced wellbore failure, such as stress-induced borehole breakouts and drilling-induced tensile fractures. Wellbore breakouts are enlargements of the wellbore wall with 180° spacing caused by localized shear failure, where the circumferential hoop stress is most compressive and exceeds the ultimate compressive strength (UCS) of the rock. In vertical wells, breakouts always form in the direction of the least principal horizontal stress. In deviated wells, the position of breakouts in a well is a function of the wellbore trajectory and the stresses acting on the wellbore. Therefore, when wellbore failures can be detected, their occurrence and characteristics (i.e., azimuth and width) can be used to determine in-situ stress magnitudes, effective rock strength, and stress orientations. In general, an abundance of stress-induced wellbore breakouts and some drilling-induced tensile fractures were detected. These fractures occurred intermittently throughout all three Unayzah formations. Cumulative length of these breakouts ranged from 86 to 142 ft in each well.

Development of Optimal Design of Solar Water Heating System by Using Evolutionary Algorithm

There are growing initiatives to promote renewable energy in Hong Kong, particularly for solar energy. In order to encourage wider application of centralized solar water heating system for high-rise residential buildings, it is important to pursue an optimal design to get significant energy-savings potential. In this regard, system optimization would be useful because it can relate to a number of design variables of the solar water heating system. The objective function is to maximize the year-round energy savings by using the solar heating against the conventional domestic electric heating. For the methodology of optimization, evolutionary programming, one of the paradigms of the evolutionary algorithm, was applied. From the optimization results, it is suggested that the solar collectors can be installed onto the external shading devices as an integrated architectural feature, since the optimal tilt angle is 21 deg and relatively flat. The optimal surface azimuth is southwest 16 deg, instead of due south. For the engineering design, both the optimal values of calorifier storage capacity and pump flow rate show that the calculations from normal design practice may not achieve an optimal performance.

A study on the intercepted insolation as a function of slope and azimuth of the surface

Monthly average daily global radiation on surfaces tilted towards the equator and also inclined at various azimuth angels are estimated for three locations in the Southern African region from reported global and diffuse radiation on a horizontal surface. The anisotropic model suggested by Hay is used in obtaining daily radiation at various slopes and orientations. Total annual radiation data are also computed for various tilt and azimuth angles and optimum tilt and azimuth angels corresponding to maximum insolation are obtained for winter, summer and annual collection. The optimum tilt and orientation reported here show some variation from those reported earlier by other investigators and the results are discussed.

Building extraction from DSM acquired by airborne 3D image

Segmentation and edge regulation are studied deeply to extract buildings from DSM data produced in this paper. Building segmentation is the first step to extract buildings, and a new segmentation method-adaptive iterative segmentation considering ratio mean square-is proposed to extract the contour of buildings effectively. A sub-image (such as 50×50 pixels) of the image is processed in sequence, the average gray level and its ratio mean square are calculated first, then threshold of the sub-image is selected by using iterative threshold segmentation. The current pixel is segmented according to the threshold, the average gray level and the ratio mean square of the sub-image. The edge points of the building are grouped according to the azimuth of neighbor points, and then the optimal azimuth of the points that belong to the same group can be calculated by using line interpolation.

Estimating the Pressure-Transient Response for a Horizontal or a Hydraulically Fractured Well at an Arbitrary Orientation in an Anisotropic Reservoir

Summary This article presents a method for finding the equivalent isotropic system for a horizontal well or a hydraulically fractured well at an arbitrary azimuth in an anisotropic reservoir. The equivalent isotropic system can then be used to calculate the pressure response of the original system. The horizontal well solution is compared with previous solutions reported in the literature. The general hydraulically fractured well case has not, to our knowledge, been presented before. This study confirms the observation by Yildiz and Ozkan1 that small deviations (up to 20°) from the optimal azimuth for a horizontal well do not have a major effect on the pressure response. Because this solution is obtained by finding an equivalent isotropic system, this study also confirms the observation by Earlougher2 that an anisotropic system cannot be identified from a single-well test.

Integrated of inclined pilot hole core with horizontal image logs to appraise an aeolian reservoir, Auk Field, central North Sea

An inclined appraisal well, 30/16-13, drilled in 1992-3 in the north of the Auk Rotliegend oil field, Central North Sea confirmed sufficient gross rock volume to justify a horizontal appraisal/development sidetrack 30/16-13S1 to assess the viability of a horizontal well development for Auk North. Close proximity of the two wells provided an opportunity for an integrated reservoir description. Core over the entire 125 m reservoir section of 30/16-13 was orientated, and tied to dipmeter data, later reprocessed into image logs. These data, plus conventional log responses, enabled a threefold subdivision of the aeolian facies including dune slipface sandstones. The sidetrack was horizontally geosteered through 625 m of reservoir, maintaining a stand-off above the field-wide free water level, and beneath the dipping Top Rotliegend structure unconformity. Careful selection of the optimal azimuth for the horizontal well track to pass up stratigraphic section maximized the number of slipface intervals encountered and preferential permeability pathways to the wellbore. Formation MicroImager (FMI) logs in the horizontal well, calibrated with core and logs from the inclined hole, enabled the characterization of the lithofacies, faults and fractures, including orientations. This detailed reservoir characterization was much greater than could be expected from either hole.

Optimal Orientation of Water‐Supply Boreholes in Fractured Aquifers

AbstractThe chance of encountering a water‐bearing fracture when boring in a hard‐rock aquifer can be maximized by drilling a borehole at an optimal inclination from the vertical, and an optimal azimuth with respect to fracture orientation. This paper describes the process of calculating the optimal borehole orientation for two common fracture patterns (orthogonal and biaxial stress‐induced), and discusses the application of the technique to a general case. It is found that, in terrains with well‐developed, transmissive vertical fracture planes, significant advantages can be obtained by drilling at large angles to the vertical.

Optimization of azimuth angle for some kinds of media on digital VCRs

A method to determine an optimum azimuth angle in a digital video tape recorder is demonstrated together with consideration made for ME (metal evaporated), MP (metal particulated), and Ba-ferrite tapes. The optimum azimuth angle is derived by comparing the value of theoretically and experimentally derived signal-to-noise ratios (SNRs) at the detecting point of a video cassette recorder with the value of theoretically derived SNR required to achieve a desired bit error rate under crosstalk interference from adjacent tracks. Not only azimuth angle but also bit length and track pitch for maximizing a real recording density are simultaneously derived by the method. The relationship between the optimum azimuth angle and orientation of the tapes is discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Symbolic Enhancement of Perspective Displays

Two exocentric azimuth judgement experiments with a perspective display were conducted with 16 subjects. Previous work has shown these judgements to exhibit a bias possibly due to misinterpretation of the viewing parameters used to generate the display. Though geometric compensations may be used to correct for the bias, an alternate technique selected in the following 2 experiments was the introduction of symbolic enhancements in the form of compass roses. It is suggested that a compass rose with 30° divisions results in overall optimal azimuth estimation accuracy when accuracy and decision time are both considered. The data also suggest that the added radial lines on the compass roses may interact with normalization processes that influence the judgement errors.

INVESTIGATION OF MAXIMUM STRESSES IN LONG, PRESSURIZED, CYLINDRICAL SHELLS

mum launch azimuths, since for this launch time the optimum azimuth is due-east. The entire trajectory is seen to lie in the reference plane, and where the trajectory terminates, the reference plane is extended by the dashed curve. For the other two launch times, the reference plane is translated and drawn through the launch site in order to yield a visualization of two-dimensional motion. Some understanding of the variation of launch azimuth can be obtained from this figure. Consider, for example, the trajectories shown for Afo = +1 hr. For the due-east launch azimuth, the trajectory is S shaped. There are two turnings or bendings of the trajectory. Near the launch site, the flight plane is turned southerly to bring the motion toward the desired plane. Towards the injection point, a second turning is necessary to bring the velocity vector as well as the position vector into the plane. Optimization of the launch azimuth is seen to alleviate the necessity for the bending around the launch site. Thus, the bending of the trajectory, i.e., its three-dimensionality, can be equated roughly with energy expenditure. This would leave one with a final conjecture. The initial bending of the plane seen for the due-east launch azimuth is necessary to direct the motion toward the desired plane, and if this were not done, burnout would occur at some point relatively remote from the reference plane. But if a coast were introduced at a sufficiently high energy level to avoid excessive descent, and if the coast were of a sufficiently long duration to allow a displacement of the order of 180°, the vehicle would approach automatically the reference plane from the other side of the earth. This may improve performance in much the same manner as did optimization of the launch azimuth.

NOTE ON REFLECTIONS FROM STEEPLY DIPPING BEDS

A brief report is given of some experimental work on known geologic conditions conducted by the Pionier Company in southeastern Poland. This is a region of steep dips, severe folding, overthrusts, and step‐faulting. The geologic conditions are first described, and this is followed by a discussion of the mathematical and physical aspects of the problem. It is pointed out that the problem is essentially one of three dimensions. Its solution ordinarily demands that the azimuth of shooting, in relation to strike, and the travel time relations at right angles to the strike, be known. But for the steep dips encountered in mountainous country, this is not always possible. Then the Time Gradient is a convenient criterion of the dip component in the direction of shooting. The problem is reduced to one of finding the time gradient in the direction of maximum dip. Curves of the time gradients are given for horizontal and for dipping beds. The method is applied to selected records and found to work well. The conclusion is reached that, where shots in different azimuths are impossible, there is an optimum azimuth, just as there is an optimum spread; but it may take much experimentation to determine where this azimuth is.