bluuebunny/crossref_metadata_2025_split huggingface dataset:
Integrating Engineering and Operations for Successful HTHP Exploratory Drilling.
Authors: Smith J. R. , Cade R. S. , Gatte R. D. 
Published: December 2007

SummaryThe Amoco Matagorda Island 636 No. 1 exploratory well was successfully drilled to 18,834 ft in 85 days. Both the depth and the drilling time were industry records for the 50-block area on trend with the well. The 357°F bottomhole temperature, required mud weights of up to 18.5 lbm/gal, more than 8,000 ft of overpressured section, more than 2,000 ft of previously unexplored section, and the historical drilling problems in the area combined to make this well a special challenge. The results validate the strategy that was developed to integrate engineering and operations as an example of how to meet such challenges successfully.This paper focuses on describing this strategy, how it was developed and applied, and the results achieved relative to previous industry performance in the area. Planning, innovation, and teamwork were the crucial components of the strategy and are discussed in detail. Specific examples of techniques, technology, tools, and our tactics for applying them are provided. These ranged from rigorous application of important industry standard practices to pure experimentation (with previously untried bit designs) and included a comprehensive effort to achieve a positive synergy within both the drilling system we assembled and our organization for its operation.
Optimal Transformations for Multiple Regression: Application to Permeability Estimation From Well Logs
Authors: Xue Guoping , Datta-Gupta Akhil , Valkó Peter , Blasingame Tom 
Published: December 2007

Summary
Conventional multiple regression for permeability estimation from well logs requires a functional relationship to be presumed. Because of the inexact nature of the relationship between petrophysical variables, it is not always possible to identify the underlying functional form between dependent and independent variables in advance. When large variations in petrological properties are exhibited, parametric regression often fails or leads to unstable and erroneous results, especially for multivariate cases.
In this paper, we describe a nonparametric approach for estimating optimal transformations of petrophysical data to obtain the maximum correlation between observed variables. The approach does not require a priori assumptions of a functional form, and the optimal transformations are derived solely based on the data set. Unlike neural networks, such transformations can facilitate physically based function identification. An iterative procedure involving the alternating conditional expectation (ACE) forms the basis of our approach. The power of ACE is illustrated using synthetic as well as field examples. The results clearly demonstrate improved permeability estimation by ACE compared to conventional parametric-regression methods.
Effect of Pressure on Improved Oilflood Recovery From Tertiary Gas Injection
Authors: Grigg R. B. , Gregory M. D. , Purkaple J. D. 
Published: December 2007

Summary
Twenty-eight tertiary gas-injection corefloods were conducted to define the pressure/recovery curves for five crude oils. These results have been compared with slim-tube recovery tests using the same five reservoir fluids. Field-scale CO2 floods have been or are currently under way in three of the studied reservoirs (S, H, and M). The other two reservoirs (F and A) have been considered for CO2 and hydrocarbon-gas injection, respectively. The results for the four CO2 injection systems consistently showed that oil recovery decreases dramatically below the minimum miscibility pressure (MMP) exactly like slim-tube tests, while the recovery in the hydrocarbon-gas injection system decreased almost linearly with decreasing pressure both above and below the MMP. To use short cores, it is expedient to use an external transition-zone generator. A method has been developed that successfully circumvents the oil resaturation problem caused by most transition-zone generators.
Influence of Syneresis on Permeability Reduction by Polymer Gels
Authors: Bryant S. L. , Rabaioli M. R. , Lockhart T. P. 
Published: December 2007

Summary
Syneresis is commonly believed to be incompatible with the application of polymer gels to reduce the permeability of porous media. In this paper, it is shown that, although the permeability of a geltreated porous medium does increase as syneresis proceeds, the degree of permeability reduction in cores remains technologically useful even when 95% syneresis is observed in bulk samples. Arguments are presented for the preferential shrinking of syneresed gel into pore throats; this model explains why permeability reduction is maintained and accounts for several other experimental results. The absence of performance penalties for syneresis has significant implications for the applicability of gels for water shutoff treatments in matrix formations. For example, it raises the possibility that polymer gels can be applied successfully in situations previously considered unfeasible because of the difficulty of maintaining gel stability, e.g., at high temperatures or in the presence of hard formation brines.
Water Control in Producing Wells: Influence of an Adsorbed-Polymer Layer on Relative Permeabilities and Capillary Pressure
Authors: Barreau Patrick , Bertin Henri , Lasseux Didier , Giénat Philippe , Zaitoun Alan 
Published: December 2007

Summary
To determine modifications of oil/water two-phase-flow properties after injection of water-soluble polymers, unsteady-state flow experiments were performed on both water- and oil-wet (silanetreated) sandstones. The same imbibition cycle (water displacing oil) under the same conditions was performed on the same core, first without any polymer and then after polyacrylamide had been adsorbed within the core. The capillary pressure was measured directly along the core by use of water- and oil-wet semipermeable membranes, while relative permeabilities were determined from the measurement of the saturation profile (by gamma ray absorption), outlet fluid production, and pressure drop.
The action of adsorbed polymer on relative permeabilities was found to be the same with both water- and oil-wet cores (i.e. a selective reduction of the relative permeability to water with respect to the relative permeability to oil). The trend was somewhat different for the capillary pressure. For the case of water-wet sandstones, the capillary pressure remained positive but increased dramatically after polymer adsorption. Because the polymer has little effect on the interfacial tension (IFT), this effect was attributed to the reduction of pore-throat size caused by macromolecule adsorption and to a possible improvement of the wettability of the core to water. For the case of oil-wet sandstone, the capillary pressure curve moved from negative to positive values, indicating that, in addition to pore-size restriction, the wettability of the core changed after polymer adsorption. This wettability change also induced a dramatic drop in residual oil saturation (ROS).
3-D Pore-Scale Modelling of Sandstones and Flow Simulations in the Pore Networks
Authors: Bakke Stig , Øren Pål-Eric 
Published: December 2007

Summary
A new method for generating realistic homogenous and heterogeneous 3-D pore-scale sandstone models is presented. The essence of our method is to build sandstone models which are analogs of actual sandstones by numerically modelling the results of the main sandstone-forming geological processes - sandgrain sedimentation, compaction, and diagenesis. The input data for the modelling are obtained from image analyses of thin section images of the actual sandstone.
The spatial continuity of the sandstone model in the X, Y, and Z directions is determined using a scale-independent invasion percolation based algorithm. The resulting spatial continuity function, which is an ellipsoid, may be used as a heterogeneity descriptor for the sandstone model. Heterogeneity analyses show that compaction reduces the spatial continuity in the horizontal direction more rapidly than in the vertical one.
The architecture and geometry of the network representation of the pore space are determined by applying various 3-D image analysis algorithms directly on the fully characterised sandstone model. A 3-D pore network which was generated from thin section data from a strongly water wet Bentheimer sandstone is used as input to a two-phase network flow simulator. Simulated transport properties for the sandstone model are in good agreement with those determined experimentally.
Ekofisk Field Reservoir Characterization: Mapping Permeability Through Facies and Fracture Intensity
Authors: Agarwal Bijan , Allen L. R. , Farrell H. E. 
Published: December 2007

Summary
The development of a strategy for the detailed three-dimensional (3D) description of permeability was a key ingredient of the recent reservoir characterization study of the Ekofisk field. Because the ultimate objective of this characterization effort was the construction of a new full-field 3D reservoir flow model, permeability and its heterogeneity received special focus. Permeability has a tremendous influence on history matching of reservoir fluid flow models and, in turn, reservoir-management decisions. This is particularly true in a mature, waterflooded field such as Ekofisk.
The Ekofisk field is a high-porosity, low-matrix permeability naturally fractured chalk. Fluid-flow characteristics of the reservoir are largely governed by the distribution, orientation, and interconnectivity of the natural-fracture system. To honor this mechanism, an algorithm was developed based on the log linear relationship between fracture spacing (intensity) data from core and well-test effective permeability. To capture the intrinsic heterogeneity and complex nature of Ekofisk field, the basic relationship between fracture intensity and permeability was modified to incorporate variations associated with (1) chalk facies (2) fracture type; (3) porosity; (4) structural location; (5) structural curvature; and (6) silica content.
To calibrate the algorithm, permeability determined from distributing total well-test flow capacity (kh) based on production log contribution was used as a tuning parameter. As a final step, geostatistical techniques were used to ensure that permeabilities derived from the algorithm matched those obtained from well-test analysis.
Productivity of Fractured Gas-Condensate Wells: A Case Study of the Smorbukk Field
Authors: Settari Antonin , Bachman R. C. , Hovem K. A. , Paulsen S. G. 
Published: December 2007

Summary
This paper describes a systematic study of the effect of condensate blockage on the productivity index (PI) of hydraulically fractured wells in a complex, highly heterogeneous reservoir containing rich gas condensate. The study was performed for the Smorbukk field offshore Norway with sophisticated simulation models. The techniques used are general, and the study findings apply as guidelines in general to fractured gas-condensate wells. Proppant fracturing is capable of restoring most of the productivity lost owing to liquid buildup. The effectiveness depends primarily on the reservoir heterogeneity, fracture length and conductivity. The relative benefits of fracturing decrease in highly heterogeneous formations.
Options for Small-Scale Sulfur Recovery
Authors: Royan Tom , Wichert Edward 
Published: December 2007

Summary
With the issuance by the Alberta Energy Resources Conservation Board and Alberta Environment of their report entitled Sulphur Recovery Guidelines for Sour Gas Plants in Alberta in August of 1988, the requirement in Alberta to recover sulfur was broadened to a sulfur content of 1 tonne/D or greater in the inlet gas to a new sour-gas treating plant. This paper reviews the processes in use for recovering sulfur from sour-natural-gas streams that have a total sulfur content of 5 tonne/D or less. These processes are the modified Claus process, the recycle Selectox process, and the reduction/oxidation processes LO-CAT and SulFerox. While the modified Claus process is used in large sulfur-recovery plants, the other processes may be more economical for sulfur recovery on a small scale. A description of the sour-gas treating and sulfur-recovery processes is given, and a comparison of estimated capital and operating costs for typical sour-gas streams is provided.
All of the above processes are in operation in North America. Operating experiences with these processes in Alberta are discussed. The quality of the end-product sulfur varies among these processes, and the options for sulfur disposal are reviewed.
A Relative Permeability Modifier for Water Control of Gas Wells in a Low-Permeability Reservoir
Authors: Tielong Chen , Yong Zhao , Kezong Peng , Wanfeng Pu 
Published: December 2007

Summary
Water control in gas wells is a major measure to enhance gas recovery. The work is concentrated on finding a highly selective polymer to reduce water production without affecting gas production from gas wells in low-permeability reservoirs. This paper presents the conceptions of residual resistance factors (RRF's) to both wetting and non-wetting phases and the laboratory experimental and field trial results of relative permeability modifiers for water control in gas wells.
On the Determination of Reservoir Pressure When Radial-Flow Conditions Are Nonexistent
Authors: Raghavan Rajagopal , Chu Wei Chun 
Published: December 2007

Summary
We present a new method to determine average pressure. This method is particularly suited for situations in which no record of the pseudoradial-flow period exists, which is the case in many low-permeability reservoirs. The assumptions of the method we propose are identical to conventional methods, except that the pseudoradial-flow period need not exist. The method may be used in channel-type reservoirs. Example illustrations are presented.
Asphalt Formation and Precipitation: Experimental Studies and Theoretical Modelling
Authors: Sahimi Muhammad , Rassamdana Hossein , Dabir Bahram 
Published: December 2007

Summary
Extensive new experimental data are presented for the amount of precipitated asphalt and asphaltene aggregates formed with crude oil and various precipitating agents, and their molecular weight (MW) distributions. A new scaling equation is proposed for predicting the onset and amount of the precipitates, which is similar to those encountered in aggregation phenomena. The scaling function takes on a very simple form, and its predictions are in very good agreement with the data. Small-angle X-ray and neutron scattering data are analyzed to delineate the structure of the asphalt and asphaltene aggregates. The analysis suggests that asphalt and asphaltene aggregates are fractal structures with well-defined fractal properties. The mechanisms that give rise to such fractal aggregates are identified, based on which a new analytical equation for the MW distribution of asphalt and asphaltene aggregates is proposed which provides accurate predictions for the data.
Modeling Asphaltene Precipitation During Primary Depletion
Authors: Nghiem Long X. , Coombe Dennis A. 
Published: December 2007

Summary
This paper describes a thennodynamic model for asphaltene that captures the behavior of asphaltene precipitation during primary depletion. Precipitation occurs above the saturation pressure, reaches a maximum value around the saturation pressure, and decreases as the pressure drops further. The precipitated asphaltene is represented as a pure solid, with the oil and gas phases modeled with an equation of state (EOS). A validation of the model",:ith exp~rimental data is reported. A study of the sensitivity of the model to different parameters IS described.
General Three-Phase Relative Permeability Model for Prudhoe Bay
Authors: Jerauld G. R. 
Published: December 2007

SummaryThis paper describes two- and three-phase relative permeability concepts important for Prudhoe Bay. It includes a three-phase relative permeability correlation that incorporates hysteresis in gas, oil, and water relative permeability as well as the dependence of relative permeability on composition and gas/oil interfacial tension (IFT). The functional forms chosen to correlate the relative permeability data were based on interpretation of the pore-level mechanisms that determine fluid flow. The three-phase correlation reduces to traditional models in various limits and is more consistent with available data and trends in the literature than previous correlations. Although this correlation was developed for Prudhoe Bay, it can be and has been applied to other mixed-wet reservoirs with changes in the input parameters. The correlation is particularly useful in situations where both compositional effects and hysteresis are important.
Hydrocarbon Production Scheduling With Genetic Algorithms
Authors: Harding T. J. , Radcliffe N. J. , King P. R. 
Published: December 2007

Summary
This paper describes the application of stochastic search techniques to the production scheduling of a group of linked oil and gas fields. The goal was to maximize the total net present value (NPV). A genetic algorithm with problem-specific crossover operators was particularly successful in this respect.
Towards Risk-Based Well Separation Rules
Authors: Williamson H. S. 
Published: December 2007

Summary
In previous descriptions of the application of quantitative risk assessment (QRA) to subsurface well collisions, several key parts of the analysis have been missing. In particular, no allowance has been made for human error, the distribution of survey errors has not been adequately investigated, and no distinction has been made between real and modeled risks. This precludes immediate application of the technique in cases where personnel or the environment are at risk.
These three problem areas each require a challenging analysis, but their resolution would provide a generally applicable risk-based well separation rule. Moreover, once such a rule were in place, there would be several options for further reducing well separations without relaxing the tolerable risk levels.
When neither personnel nor the environment are at risk, the problems with the basic analysis are less acute. The technique is currently being applied operationally in these cases.
Induction Log Shoulder-Bed Corrections to Anisotropic Formations and the Effect of Shale Anisotropy in Thinly Laminated Sand/Shale Sequences
Authors: Hagiwara Teruhiko 
Published: December 2007

SummaryWe examine induction log responses to layered, dipping, and anisotropic formations analytically. The analytical model is especially helpful in understanding induction log responses to thinly laminated binary formations, such as sand/shale sequences that exhibit macro-scopically anisotropic resistivity. We discuss two applications of the analytical model.In one application, we examine special induction log shoulder-bed corrections for use when thin anisotropic beds are encountered. It is known that thinly laminated sand/shale sequences act as macroscopically anisotropic formations. Hydrocarbon-bearing formations also act as macroscopically anisotropic formations when they consist of alternating layers of different grainsize distributions. When such formations are thick, induction logs accurately read the macroscopic conductivity, from which the hydrocarbon saturation in the formations can be computed. When the laminated formations are not thick, proper shoulderbed corrections (or thinbed corrections) should be applied to obtain the true macroscopic formation conductivity and to estimate the hydrocarbon saturation more accurately.We use the analytical model to calculate the thinbed effect and to evaluate the shoulder-bed corrections. We show that the formation resistivity and, hence, the hydrocarbon saturation are greatly overestimated when the anisotropy effect is not accounted for and conventional shoulder-bed corrections are applied to the log responses from such laminated formations.In another application, we examine the effect of shale anisotropy in thinly laminated sand/shale sequences. How do induction logs respond to such laminated formations when shale laminae are anisotropic? How accurate are the estimates of the sand-laminae resistivity and of the hydrocarbon saturation in these sand laminae? To answer these questions, we used the analytical model to examine the effect of shale lamina anisotropy on induction log responses in thinly laminated formations. We learned that the macroscopic conductivity of a laminated formation is determined uniquely by the sandlaminae conductivity and the anisotropic shale conductivity, if the sand fraction is known. We also found that the sand resistivity estimate depends on the value of shale resistivity and the dip angle, if the shale is assumed to be isotropic and if the sand fraction is known. When the sand fraction is not known, the sand resistivity and the sand fraction can be estimated if the set of horizontal and vertical macroscopic resistivities is known. In this case, the sand resistivity tends to be overestimated if the shale anisotropy is not accounted for. On the other hand, the sand fraction estimate is generally insensitive to the shale anisotropy, except for low sand-laminae resistivity (Rsd/Rsh &lt; 5).
Application of Sequence Stratigraphic Reinterpretation of Lower Lagunillas Member to Further Development of Bloque IV, Lake Maracaibo, Venezuela
Authors: Bryant I. D. , Herron M. M. , Villarroel H. Gamero de 
Published: December 2007

Summary
Discovered in 1955, the Lower Lagunillas member reservoir of the Miocene Lagunillas formation of Bloques III and IV of the Bachaquero field was originally estimated to contain 2 billion barrels of oil. This reservoir interval traditionally has been interpreted to have been deposited in a delta plain setting and to comprise three reservoir subdivisions that were developed as a single drainage unit. Field performance, however, has indicated that the reservoir is more complex; the present study was initiated to provide a revised development strategy.
Sedimentological interpretation of four cored wells has led to the development of a new model of deposition in tidally influenced lower delta plain and delta-front settings. This model is supported by Fourier transform infrared (FT-IR) measurement of clay concentrations and prompt neutron capture boron measurements that are indicative of a brackish water-depositional setting. We used this geological model to guide correlation of wireline logs from 46 wells in the central part of Bloque IV and to provide a high-resolution sequence stratigraphic model of the Lower Lagunillas reservoir. Eleven genetic layers are identified that are separated by locally developed intraformational seals into up to eight drainage units. High permeability, tidally influenced channel-fill sands have acted as preferential conduits for gas influx, leaving bypassed oil in lower quality sands that were deposited as tidal deltas and bars. This reservoir model has been supported by re-examination of production data and by openhole measurements in a recent infill well and cased- hole logging of two other wells in the study area. The new model will form the basis for redevelopment of the Lower Lagunillas reservoir to increase recovery further from this mature field.