bluuebunny/crossref_metadata_2025 huggingface dataset:
A Semi-Analytical Approach for Productivity Evaluation of Wells with Complex Geometry in Multilayered Reservoirs
Authors: Basquet R. , Alabert F. G. , Caltagirone J. P. , Batsale J. C.
Published: December 2007

We present a new approach to solve the problem of complex wells located in layered reservoirs with crossflow.

First, well path is discretized into a carefully chosen series of source points. Secondly, pressure solution for each source point is obtained in the Laplace domain anywhere in a rectangular reservoir, where crossflow is permitted between layers and with possibly mixed boundary conditions (no-flow or constant pressure). We used the Fourier transforms in the space-variables after removing the time-variable by the Laplace transformation. The problem is reduced to a matrix product to solve in the transformed domain.

The above method is validated through comparisons with known line source solutions and numerical simulations.

It can be used to compute the pressure distribution within a well with complex geometry in a stratified bounded reservoir under the assumption of infinite well conductivity. The well can be located anywhere in the reservoir. Boundaries can be no-flow or constant pressure. Last, variable skins along the well-path can be imposed.

An application on a field located in the deep offshore of the Gulf of Guinea demonstrates the great value for wells design optimization in the context of complex heterogeneous reservoir where classical analytical approaches are typically inappropriate.
New Solutions for Pressure Transient Response for a Horizontal or a Hydraulically Fractured Well at an Arbitrary Orientation in an Anisotropic Reservoir
Authors: Spivey J.P. , Lee W. John
Published: December 2007

This paper 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 for constant rate production or the rate response for constant pressure production.

The horizontal well solution is compared with previous solutions reported in the literature. The general hydraulically fractured well case has not, to the knowledge of the authors, been presented before.

This study confirms the observation by Yildiz and Ozkan that small deviations (up to 20 degrees) 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 Earlougher that an anisotropic system cannot be identified from single-well test.

P. 627
Worldwide Turbidite Exploration and Production: A Globally Immature Play with Opportunities in Stratigraphic Traps
Authors: Pettingill Henry S.
Published: December 2007

An analysis of 925 discoveries from 54 basins worldwide demonstrates the importance of turbidites to future petroleum Exploration and Production. A plot of cumulative worldwide turbidite reserves versus time is currently at a slope maxima, indicating a globally immature play with significant remaining opportunity. 41 turbidite giants >500 MMBOE) illustrate the relatively recent importance of turbidites: in the 75 years before 1970, 14 BBOE was discovered in 11 fields, whereas since 1970, 34 BBOE have been found in 30 fields.

Cumulative turbidite reserve's plots do not always follow the pattern typical of most plays, where larger fields are discovered early. The steepest climb in cumulative turbidite reserves usually results from traps with a stratigraphic component, which are often discovered later. This dominance of stratigraphic trapping occurs in various basin settings, shown here by the 5 basins with highest ultimate turbidite reserves: the North Sea, Campos, Gulf of Mexico, Los Angeles and San Joaquin basins. Turbidite giants further demonstrate the importance of the partial stratigraphic trap: 25% of the reserves come from structural traps, 9% from stratigraphic traps. and 66% from combination structural-stratigraphic traps. So if a turbidite play is judged solely on its structural prospect inventory, then the reserve potential will be underestimated. Additionally, basins with turbidite production limited to structural traps may have a bright Exploration and Production future.

As most major turbidite hydrocarbon provinces are in basins that produce from other reservoir types, lessons from past exploration could be applied to major producing basins which contain turbidites but lack significant turbidite production - even in basins that are in a relatively mature state of Exploration and Production.

P. 637
Propant Free-Shear Dilation: An Emerging Techology for Exploiting Tight to Ultra-Tight Gas Resources
Authors: Narayan S.P. , Yang Z. , Rahman S.S. , Jing Z.
Published: December 2007

In recent years there has been a growing interest in applying proppant free fracturing technique to stimulate tight to ultra tight gas reservoirs. The permeability enhancement mechanism for proppant free fracture stimulation has, in the HDR geothermal industry, been long recognised as shear dilation induced by elevated fluid pressure. Passive micro seismic monitoring technique has been well established in the HDR geothermal industry for imaging growth and geometry of reservoirs created by proppant free stimulation. Both field evidence from seismic monitoring and 3D stochastic stimulation modelling show clearly the volumetric nature of the stimulated rock mass with the proppant free stimulation technology. The detailed reservoir geometry, however, is complex due to interaction of natural fractures and in-situ stress regimes, and may be controlled either by dominant fracture sets or in-situ stresses. There exists a threshold stimulation fluid pressure above which permeability of stimulated fractures increases rapidly with increase in fluid pressure. The threshold pressure is inversely related to the deviatoric stresses. In regions with strong deviatoric stresses such as in Central Australia, the threshold stimulation pressure is expected to be low. Thus, creation of a large volume of reservoir by relatively low stimulation pressure could make the proppant free stimulation a viable alternative to conventional massive hydraulic stimulation from both technical and economical stand point.

P. 687
Stabilizing Wellbores in Unconsolidated Formations for Fracture Stimulation
Authors: Nguyen P.D. , Brumley J.L. , Dewprashad B.T. , Dusterhoft R.G. , Weaver J.D.
Published: December 2007

A wellbore stabilization system incorporating fracture stimulation has been developed and modeled in the laboratory for unconsolidated and dilatant formations. The profile of resin leakoff and penetration depth into the formation is relatively dependent on the pattern of perforations. Use of dissolvable particulates as a fluid-loss control agent proved to be effective in diverting resin, resulting in a uniform distribution of resin over the highly varying permeability interval. A significant drop in permeability of the near-wellbore area occurred after the resin treatment, but high productivity was re-established by connecting the wellbore with the untreated formation through highly conductive fractures. During companion testing of the resin-consolidation technique, the unconsolidated sand pack became a competent formation with compressive strength in excess of 2,000 psi. This competent material will be affected less by high drawdown pressures and stress cycling during production/shut-in cycles. The injection pressure required to fracture the consolidated wellbore showed an increase when compared to that of the untreated wellbore. Stress levels existing in the formation were shown to control the number and direction of generated fractures bypassing the consolidated zone.

P. 703
Applications and Limitations of Advanced Steel Body PDC Bit Technology
Authors: Smith L.M. , Perrin V.P. , Al-Habsi M. , Mody F. , Delwiche R. , Akin E.
Published: December 2007

New steel body PDC bit technology is shown to enhance drilling performance in a range of applications previously limited to matrix body bits. Specific aspects of the technology are detailed, including various proven design features, and unique manufacturing and materials treatment. In addition, the paper addresses the impact of increasing energy available at the bit face through utilization of a new hydraulic jet technology in combination with the advanced features of steel body PDC bits. Case histories are included to describe the application range of the new steel body bits, in terms of both drilling performance and economic impact.

P. 733
Gear Reduction Turbodrills Improve Drilling Results
Authors: Derkach N.D. , Krutik E.N. , Korotaev Yu. A.
Published: December 2007

The subject of the paper is development of a new class downhole hydraulic motors - gear reduction turbodrills, results of their application, advantages over the other motor classes. The first gear reduction turbodrill TRM-195 developed is widely used in oil and gas well drilling in Russia. It was the gear reduction turbodrill that drilled more than 3,5 mln metres of rocks. The best results were obtained in its conjunction with rolling-cutter bits of Western companie's production while well completion in West Siberia. Heat-resistant version of the turbodrill was successfully used in drilling the world deepest Kola well (12260 m). Based on the experience gained new designs and modifications of the gear reduction turbodrills are being developed to improve their performances while drilling directional and horizontal wells. They should be most advantageous in enhanced temperature wells (exceeding 150- 200 C) using PDC bits.

P. 755
StarWars Laser Technology Applied to Drilling and Completing Gas Wells
Authors: Graves R. M. , O'Brien D. G.
Published: December 2007

This paper describes results of the first phase of a Gas Research Institute (GRI) funded research program. The overall purpose of this research is to advance a fundamental change in the method currently used to drill and complete natural gas wells applying the U.S. Defense Department's StarWars laser technology. Results of tests conducted at the U.S. Air Force and the U.S. Army's high power laser research facilities are presented.

Initial testing on reservoir rocks conducted with the Mid Infrared Advanced Chemical Laser (MIRACL) at the U.S. Army's High Energy Laser Systems Test Facility at White Sands, New Mexico, showed the potential for laser drilling. The laser beam drilled at a speed that indicates penetration could be increased by more than 100 times current rates.

Planned testing for the next phase of this research is to use the Chemical Oxygen-Iodine Laser (COIL) high powered laser invented in 1977 by the U.S. Air Force Research Laboratory in Albuquerque, New Mexico, for air-to-air defense. COIL has gained notoriety as an airborne laser tactical weapon capable of tracking and destroying missiles.

An annotated bibliography was developed for the GRI that comprehensively reviews published laser-rock interaction, current drilling research, and technical data related to laser applications in non-reservoir rocks.1 Developing commercial applications of StarWars laser technologies has commenced not only in the U.S., but also in Russia and the former Soviet Union.
Wellbore Stability: A New Conceptual Approach Based on Energy
Authors: Santos Helio , Diek Adel , Roegiers Jean-Claude
Published: December 2007

The conservation of energy principle is applied to analyze wellbore stability. A conceptual model and simple method to quantify the energy associated with the main events during drilling are proposed here. However, evaluation of the consequences in terms of damage to the rock requires specially designed tests to determine the response of the rock in terms of energy. This approach can explain the failure mechanisms usually observed in laboratory tests and most of the problems faced in the field. In view of this new approach, adequate solutions to effectively alleviate current instability problems are discussed. Successful field cases are described, demonstrating the validity of the suggested failure mechanisms.

P. 805
Modeling Relative Permeability Effects in Gas-Condensate Reservoirs
Authors: Pope G.A. , Wu W. , Narayanaswamy G. , Delshad M. , Sharma M. , Wang P.
Published: December 2007

Many gas condensate wells show a significant decrease in productivity once the pressure falls below the dew point pressure. This significantly decreases the productivity of very high rate gas wells in many of the world's largest hydrocarbon reservoirs. A widely accepted cause of this decrease in productivity index (PI) is the decrease in gas relative permeability due to build up of condensate in the near weIlbore region. Predictions of well inflow performance require accurate models for the gas relative permeability as a function of interfacial tension (IFT) between the gas and condensate phases (actually it should be trapping number rather than IFT). Since these relative permeabilities depend on fluid composition and pressure as well as condensate and water saturations, a model is essential for both interpretation of lab data and for predictive field simulations. The key to such a gas condensate relative permeability model is the dependence of the critical condensate saturation on the capillary number or its generalization called the trapping number. We have made careful comparisons of such data with a capillary trapping model and have found that we can match these data with a simple two-parameter model. We then developed a general scheme for computing the gas and condensate relative permeabilities as a function of the capillary trapping model and with only data at low trapping number (high IFT) as input and have found good agreement with the experimental data in the literature. We then used this model and typical parameters for gas condensates in a compositional simulation study of a single well to better understand the PI behavior of the well and the significance of the condensate buildup.

P. 643
How to Include the Capillary Number in Gas Condensate Relative Permeability Functions?
Authors: Blom S.M.P. , Hagoort J.
Published: December 2007

The important role of near-miscible relative permeability functions in the formation of a retrograde condensate zone around the well bore is well established. The functions depend on the ratio of viscous to capillary forces on a pore scale, denoted by the capillary number. A large number of methods have been proposed for including the capillary number in the gas condensate relative permeability functions.

We have reviewed and analyzed fifteen different methods. These can be divided into two classes:using Corey functions in which the Corey coefficients are interpolated between immiscible and miscible limits, andinterpolation between integral immiscible and miscible relative permeability curves.

In both methods the interpolation is weighted by capillary number dependent functions. From the reviewed methods we have distilled three different weighting functions that are most suitable. We have calibrated the correlations to four experimental data sets. As the capillary number we have used.

The results show that the weighting function proposed by Whitson and Fevang is the most convenient; this function covers the entire range of capillary numbers, and is able to reproduce the most important aspects of the dependence of relative permeability on the capillary number with a limited number of parameters. The function can be used for the interpolation of Corey coefficients as well as of integral relative permeability curves.

P. 661
Compositional Grading in the Ghawar Khuff Reservoirs
Authors: Temeng K.O. , Al-Sadeg M.J. , Al-Mulhim W.A.
Published: December 2007

The paper presents the results of a study to investigate the variation of gas composition and key PVT properties with depth in the Khuff carbonate reservoirs of the Ghawar field in Saudi Arabia. The study was performed as part of a larger effort to characterize the reservoir fluids for compositional simulation and development planning. Laboratory PVT reports on over twenty appraisal wells were used as a basis for the study.

It was found that both condensate content and hydrocarbon compositions decreased with depth and/or temperature while acid gas composition increase with depth. The composition of hydrogen sulfide varied from zero, at a threshold depth and temperature, to over five mole percent at greater depths. The observed variations of composition with depth were contrary to what would be expected from gravity-chemical equilibrium considerations.

We propose that the dominant process for compositional grading in the Khuff is the generation of hydrogen sulfide by thermo-chemical reduction of sulfate. This process is believed to occur at temperatures above a threshold value (about 270 0F for the Ghawar Khuff), and utilizes hydrocarbons as one group of reactants. Thus, as is shown in the paper, hydrogen sulfide composition increases with depth at the expense of hydrocarbons in a way that upsets the effect of gravity- chemical equilibrium.

P. 685
Targeting of New Wells Through an Integrated Characterisation of the Basement Reservoir in Zeit Bay Field
Authors: Kamal Mohamed , Ismail F. , Fattah Kh. A. , Khairy M. , Sayouh M.H.
Published: December 2007

The Zeit Bay field consists of sedimentary reservoir units partially overlying a tilted block of fractured basement reservoir. The field has a complex combination drive mechanisms including a secondary scheme of gas re-injection into the original gas cap. One of the major problems was to define the fracture pattern of the reservoir. The main objective of this paper is to present a method of integrating multidisciplinary data to determine and characterise the fracture pattern along the basement rock. A relationship between the fracture pattern and producing zones identified from the production log interpretation was established. Better definition of the fracture pattern improves the well trajectory in order to intersect more fractures for optimum sweep. An extensive fracture analysis was performed using fracview data from FMS (Formation Micro Scanner) in four wells. The obtained data were insufficient for the fracture characterisation across the field. A relationship between fracview data and conventional log data was derived. This relationship was applied to predict fracture porosity in the 22 remaining wells (without FMS). The prediction of cut off parameters (effective and fracture porosity) was improved by detailed cornparative analysis of logs, well tests, and production data. Geological analysis of the basement reservoir were performed and integrated with the analysis of basement surface outcrops at Gebel El Zeit, which exhibited well-defined fracture and joint network to the main Gulf of Suez trend. Maps of reservoir properties were generated and compared to the trends observed on the production data maps. The understanding of the reservoir using this integrated approach successfully helped to target new wells in the basement reservoir.

P. 699
Fieldwide Integrated Waterflood Development of a Complex Paralic Clastic Reservoir, Upper Burgan Formation, North Kuwait
Authors: Abdullah F. , Conway P.I. , Wethington W.B. , Morrison N.H. , Al Saig T. , Nemaflallah M. , Al Eidan A. , Al Qabandi S.
Published: December 2007

The Upper Burgan reservoir is a major productive interval in both the Raudhafain and Sabiriyah fields, located in Northern Kuwait. A fivefold increase in production is planned from this reservoir through the implementation of a fleIdwide watefflood development plan.

Dynamic reservoir performance data has been combined with sedimentological studies and 3D geological modelling to evaluate the dynamic complexity of the reservoir during the depletion phase. Due to limited aquifer support, a frill field waterflood development plan is to be implemented, with seawater injection scheduled to commence in 1999. The evaluation and understanding of key dynamic reservoir parameters such as productivity, injectivity and connectivity have been shown to be of critical importance in the planning of the waterflood project.

Although waterflood development will initially commence with a peripheral waterflood scheme on Raudhatain, it is expected that the ultimate development will constitute a patterntlood of both reservoirs, in common with analogue complex paralic clastic systems. The Raudhatain and Sabiriyah waterflood development plan therefore places much emphasis on flexibility and cost optimisation. Integration of this development with that of the larger, shallower Mauddud carbonate reservoir has been identified by alignment of the associated waterflood grids such that each well location may be an injection or offlake point for both reservoirs. Grid alignment provides maximum flexibility to each reservoir, accelerates drilling in the Upper Burgan, and reduces ultimate drilling expenditure by as much as 80 wells. In essence, the Upper Burgan reservoir is developed for the incremental cost of a dual wellhead, packer and additional tubing string.

P. 727
Determination of Geostatistical Parameters Using Well Test Data
Authors: Gautier Yann , Noetinger Benoit
Published: December 2007

We have set up a general framework to obtain estimations of the geostatistical parameters (GP) such as the correlation length, lc and permeability variance, ln from well test data. Most often, in practical studies, the GP are estimated using geological and petrophysical data, but in a lot of cases, these data are too scarce to give high confidence results.

The method was tested using synthetic well-test data performed on some training images, and correct estimations of the underlying correlation length, lc and permeability variance, ln were recovered. Once the GP are estimated, other well established techniques can be used to get well-test matched reservoir images consistent with the geostatistical model. In practical applications, excellent well test data are needed, and the method should be improved using multiple well test data.

P. 669
An Assessment of Lateral Variability of Geological Parameters Using Modal and Geostatistical Analysis of Outcrop Analog
Authors: Misra Debasmita , Schatzinger Richard A. , Cil Murat , Wheeler John R. , Fite M. Jill
Published: December 2007

Spatial variations in petrophysical properties have been described for interwell scale outcrop analogs to subsurface reservoir facies in the marginal marine upper Almond formation near Rock Springs, Wyoming. The objective of this study was to determine interwell scale lateral trends in heterogeneity that can be translated to nearby analogous reservoirs.

More than 1,600 one-inch diameter plugs were collected for petrophysical analysis from outcropping tidal delta, tidal channel and foreshore facies. These facies comprise reservoir quality sandstones in the Greater Green River Basin east of the Rock Springs Uplift. Modal analysis of 78 thin sections provided compositional and packing parameters.

Porosity loss in outcrop and near-outcrop tidal channel sandstones was due to both compaction (COPL) and cementation (CEPL), whereas porosity loss in tidal delta and shoreface sands was dominated by compaction. For all three facies a correlation can be found between increased intergranular volume (IGV), carbonate cements and CEPL if petrographic and petrophysical properties are first sorted according to IGV. In contrast, increased IGV correlates negatively with porosity, COPL, grain contact index, compaction index, and relative amount of lithics.

Geostatistical analysis of the petrophysical data was undertaken to determine its distribution structure, characterize lateral continuity and predictability within this system. Samples from equivalent facies at different geographic locations show geostatistical continuity although they were often found to be statistically dissimilar. Results of geostatistical analysis, therefore, are representative of the internal architecture of the facies studied. Although the statistics of reservoir properties are geographically variable, the data can be used in a predictive sense because it is geostatistically consistent in terms of variance and continuity of parameters. Geostatistical trends interpreted from the variogram analysis were imposed by ordered internal facies architecture. For our data set, oscillations beyond the variogram range could be related to the distribution of bed set boundaries.

P. 683
From Well Data to 3D Models: Determination of the Critical Path in the Process of Characterization of Reservoirs
Authors: Rolando J.-P.
Published: December 2007

At any stage of hydrocarbon field life, well data is obviously the key parameter to build realistic 3D models of reservoir properties.

Usually, reservoir models are built based on available data although it is not necessarily the optimum data for the field to be modelled. The key heterogeneity, that drives flows in the reservoir, may not have been extensively characterized by available data.

The objective of this paper is to propose an approach that takes into account the geological heterogeneity early on during the study in order to anticipate appraisal requirements and optimize rock-type distribution in reservoir models. In fact, it consists of finding the critical path: a better characterization and a more rapid diagnosis.

The method is illustrated based on various examples. It differs depending on whether the reservoir is still in the appraisal phase or already in production. Similarly, tools and techniques to be used are different according to the type of geological heterogeneity: sandy clastic reservoirs, fractured/karstified reservoirs, mixed reservoirs (clastics and carbonates, clastics and fractures)… In each case, different types of data are needed to characterize key heterogeneity. The diagnosis made on the cases given in the examples shows that an optimum interpretation is achieved when data is representative of the sampled medium.

P. 711
3D Modeling form Seismic to Fluid Flow Simulation: A Case Study
Authors: Samson P. , Casaux J.-M. , Cavailles B. , Larribau E. , Morandini F. , Biondi P. , Calassou S. , Janodet D. , Chautru J.-M. , Legrand X. , Fainaud J.-F.
Published: December 2007

The benefit of a 3D Modeling chain in Exploration Production is demonstrated on a real case study. It consists in constructing a Shared Earth Model integrating data and interpretation from geophysicists, geologists and reservoir engineers. Fast and easy updating of consistent 3D information is a key aspect. The shared earth model is the integration of the following speciality models:3D Structural Model3D Sedimentary Model3D Reservoir Model

As it contains all reservoir data, it is the reference model for:–Integrating new data–Integrating analysis form structural unfolding, foward sedimentary modeling,…–Checking new or alternative interpretations–Uncertainties–. . .

This case study highlights that a consistent model can only be achieved through a full 3D interdisciplinary team work.

P. 741
Combined Magnetic Resonance Relaxation and Imaging for Quantitative Determination of Matrix and Vugular Porosity in Carbonate Cores
Authors: Borgia G.C. , Bortolotti V. , Fantazzini P.
Published: December 2007

A method is presented to characterize the internal structure of full-size carbonate cores by combining nuclear magnetic resonance relaxation and imaging techniques (Relaxation-Tomography, RT). In addition to usual imaging techniques, a method for obtaining images as relaxation time maps was developed. An operational definition of matrix porosity based on the RT technique is presented, which has the advantage of taking into account the pore connectivity and which therefore seems to be useful in describing the flow properties of the rock. Several internal images were obtained as H nuclei density and relaxation time maps on a set of vugular and microporous carbonate cores saturated with water. From RT maps the histograms of relaxation times of selected internal regions of interest can be obtained. Reference measurements on smaller samples were performed by means of a specialized NMR relaxometer, and the reliability of the distributions of relaxation times from RT maps was confirmed. The matrix porosity was determined by combining voxel by voxel information from porosity and relaxation time maps. This investigation was performed on some meters of cores in all. In the samples examined, all from the same outcropping reservoir, the matrix porosity averages about 30% of the total porosity, with a threshold for the matrix pore space of the order of a micron or a few microns. The results indicate this approach to be a very promising technique for obtaining, among other things, basic structural information on undisturbed full-size cores. The advantages are twofold. On one hand, this technique furnishes a cost- and time-saving method of work. On the other, there are technical advantages of specificity to the phenomena involved and also the ability to select isolated regions of interest within a core. This method can be useful when it is necessary or convenient to investigate some internal parts of the cores, without any cut or disturbance. Another promising opportunity lies in the possibility of enhancing the knowledge of petrophysical properties by avoiding the effects of the mud-invaded zone of the core.

P. 751
Integrating Static and Dynamics Surveillance Data to Characterize Naturally Fractured Reservoir: A Case study of Baka Oil Field
Authors: Zhang Yonggui , Wu Ying , Ma Xiaojuan , Chen Mingqiang
Published: December 2007

Waterflooding of Baka Oil Field is dominated by natural fractures. Based on core and outcrop observation and fracture identification from logging, the static geological model of fracture distribution has been set up by studying fracture geometry and basic characteristics (orientation, aperture, extent, density, porosity and permeability). The fracture mineralization features and the factors that determine the occurrence of fractures were also studied, which include the degree of folding and/or faulting, in-situ stresses, rock properties and bedding thickness, etc.

Due to small borehole-scale and difficulties to map some factors which determine open and permeable fractures, the static model may not be representative of the large-scale fracture network which will determine reservoir performance, thus dynamics production data are integrated to get a good understanding to fracture's influence. The productivity index of per meter reservoir (Jo, ton/m.MPa.m) is used to characterize natural fractures, For production well, Jo is calculated from dynamic surveillance data directly. But for every injection well, the injectivity index of per meter reservoir (Jw) is estimated from injection data firstly, then Jo is calculated from the Jo/Jw ratio, this ratio is estimated from several actual wells which were switched from production to injection. In order to make the ratio Jo/Jw convincing, further discussion that involve Krw (Sor) / Kro (Swi) was made. Finally geostatistical method was used to distribute the productivity index. The dynamic index map matches the permeability of several wells estimated from well testing very well, and a good explanation about breakthroughs is derived, but some differences from static model still exist.

P. 757
Well Log Characterization of Sediment Porosities in Gas-Hydrate-Bearing Reservoirs
Authors: Collett T.S.
Published: December 2007

With growing interest in natural gas hydrates, it is becoming increasingly important to be able to determine the volume of gas hydrate and included gas within natural gas hydrate accumulations. Gas volumes that may be attributed to gas hydrates are dependent on a number of reservoir parameters, one of the most difficult reservoir parameters to determine is porosity. Well logs often serve as a source of porosity data; however, well-log calculations within gas-hydrate-bearing intervals are subject to error. The well-logging devices that show the greatest promise of yielding gas hydrate reservoir porosities are the gamma-gamma density and neutron porosity logs. Well log response modeling has revealed that under most conditions, the bulk-density of a water-bearing sedimentary section is almost identical to the bulk-density of a gas-hydrate-bearing sedimentary section as measured by a gamma-gamma density logging tool. At relatively high porosities (O>40%) and gas-hydrate saturations (Sh>50%), however, the downhole log derived bulk-density porosities need to be corrected for the presence of gas hydrate. A neutron well-log response computer simulator, SNUPAR, has been used to calculate nuclear transport and capture parameters for various gas-hydrate-bearing reservoirs. The calculated thermal neutron capture cross section of various hypothetical gas-hydrate-bearing reservoirs indicates that methane hydrate has little effect on neutron porosity measurements within "normal" reservoir conditions (O<40%) and low gas-hydrate saturations (Sh<50%). Within this study, density porosity and neutron porosity nomographs have been developed with which it is possible to correct for the effect of high gas-hydrate saturations on the log derived porosities. In the field verification phase of this study, downhole density and neutron porosity log data (in some cases corrected for the presence of gas hydrate) have yielded accurate porosities for gas-hydrate-bearing reservoirs on the North Slope of Alaska.

P. 765
Automated Fracture Detection on High Resolution Resistivity Borehole Imagery
Authors: Ye Shin-Ju , Baviller Philippe
Published: December 2007

This paper proposes a method to detect fractures on High Resolution Resistivity Borehole Imagery. The method provides with quantitative parameters, such as length and contrast of the fractures that can be processed with conventional logs to help characterize reservoir nature and behavior.

Thanks to the auto-optimization of the algorithm, this method is easy to operate, does not require expertise and can be used in drilling operation, on the site, in the meantime between log acquisition and casing perforation.

The method takes advantage of the fact that:–fractures are planar features secant to the stratification planes and exhibit high resistivity contrast.–stratification planes represents the dominant orientation of planar features that are seen on HR resistivity borehole imagery and, based on this characteristic, they can be detected using statistical analysis of the full image (The method is described on SPWLA logging Symposium transactions 1997, paper O).

After detection of the stratification planes, images are processed to filter out the stratification planes and normalize the background, thus making more visible the fracture planes. Fractures segments are detected on each "pad" images using "depth-first search" algorithm to find "min-cost path" and then selected according to length, contrast, linearity and visibility criteria. An image displaying the fracture segments and the associated quantitative parameters is produced. Detailed field examples are used to illustrate the results obtained in different types of lithology.

P. 777
Dynamic Displacement Measurement of Three-Phase Relative Permeabilities in Berea Sandstone Cores
Authors: Siddiqui Shameem , Yang Jiansui , Ahmed Mahbub
Published: December 2007

The measurement of three-phase relative is often a difficult and time-consuming process. To this date only a handful of papers can be found in the literature on the measurement of three-phase relative permeabilities. Grader and O'Meara developed an unsteady-state technique for measuring three- phase relative permeabilities by extending the Buckley Leverett theory to three phases. The validity of this new unsteady-state technique has been verified recently for three immiscible liquids in a glass-bead pack with the help of a medical CT-scanner (Siddiqui and Siddiqui et al.) However, this new technique has not been applied to measure the three- phase permeabilities of a rock -fluid system similar to that of a typical petroleum reservoir. This present study focuses on the application of the extension of the Buckley-Leverett theory for measurement of three-phase relative permeabilities for a brine- oil-gas system in Berea sandstone cores (permeability range 100-400 md). Several experiments were conducted using a specially designed coreflooding unit in which pressure at six locations along the core and flow rates are recorded continuously with a computerized data acquisition system. The three-phase flowpath used for this study was dynamic gas injection into the cores having a different initial water and oil saturation each time. Three-phase relative permeability data derived this way were used in a simulator to predict the recovery curves. Results show a good agreement for the different cases studied. Comparison is also made between these data and the data from experiments done with three immiscible phases (Siddiqui).

P. 759
Detection of Critical Flow Leaks in Deepwater Gas Flowlines
Authors: Scott Stuart L. , Yi Jinghai
Published: December 2007

Detection of hydrocarbon leaks from deepwater subsea flowlines represents a special challenge to both the oil and gas industry and regulators. The lack of inlet flow rate measurements, combined with an order-of-magnitude increase in gas solubility, limited access, ultra high flowrates and deepwater currents, is anticipated to compel new testing, inspection and monitoring methods for deepwater flowlines. This paper presents a leak detection technique based on routine production data, i.e. inlet and outlet pressure and outlet flow rate. This method is particularly valuable when inlet flow rate measurements are either unavailable or are of low accuracy. Based on the gas well backpressure technique, the proposed method detects changes in pipeline frictional losses resulting from a leak. Field-scale verification of the proposed method was obtained using the LSU 9,460 ft. horizontal flowloop made of 4 1/2 inch drillpipe. Multi-rate tests were conducted using methane at 650 psig with fixed diameter leaks of 1/8, 1/4 and 3/8 inches placed at the midpoint of the flowloop. The proposed method is shown to be effective in detecting leaks and, while location of the leak is also possible, it will likely require a large number of rate/pressure points to be useful. Based on this method a map has been developed that indicates what size of leak is detectable for a given set of field instruments and flow conditions.

P. 793
More Than 12 Years of Experience with a Successful Conformance-Control Polymer Gel Technology
Authors: Sydansk R.D. , Southwell G.P.
Published: December 2007

In this paper, we discuss and describe our extensive experience with the widely applied and quite successful Cr(III)-carboxylate/acrylamide-polymer (CC/AP) gel technology for use in oilfield conformance-control, sweep-improvement, and fluid-shutoff treatments, along with briefly reviewing the gel technology's development. Chromic triacetate is the often- preferred chemical crosslinking agent used in conjunction with this polymer-gel technology. The CC/AP gel technology, which was conceived in late 1984, is characterized as having a robust gel chemistry and as being highly insensitive to petroleum reservoir environments and interferences. This gel technology has been employed in over 1,400 conformance- control treatments worldwide. Highlights of illustrative field applications and results involving the CC/AP conformance- control gel technology are presented. An overview of what a decade-plus of experience in developing and applying the CC/AP gel technology has taught us is discussed. This includes discussion of: classifying and distinguishing conformance problems and treatments, attributes of good candidate wells and well patterns for gel conformance-control treatments, requirements that must be met in candidate wells and well patterns in order to achieve success, gel treatment elements that must be successfully implemented in order to achieve success, guidelines where conformance polymer-gel treatments are most successfully applied, risks and pitfalls of gel conformance treatments, and quality control issues.

P. 841
Validation of Gravity-dominated Relative Permeability and Residual Oil Saturation in a Giant Oil Reservoir
Authors: Edwards J.T. , Honarpour M.M. , Hazlett R.D. , Cohen M. , Membere A. , Pebdani F. , Clayton C. , Al-Hussainy R.
Published: December 2007

This paper was prepared for presentation at the 1998 SPE Annual Technical Conference and Exhibition held in New Orleans, Louisiana, 27-30 September 1998.
Phase Diagram of fully Developed Drainage: A Study of the Validity of the Buckley-Leverett Equation
Authors: Yortsos Yannis C. , Xu Baomin , Salin Dominique
Published: December 2007

Despite the significant progress made in recent years, a fundamental understanding of immiscible displacements at the macroscale is lacking. In this paper we use a version of percolation theory, based on Invasion Percolation in a Gradient, to connect drainage processes at the pore-network scale with the displacement at the macroscale. When the mobility ratio M is sufficiently small, the displacement is stabilized and can be described by Invasion Percolation in a Stabilizing Gradient. In the opposite case, the displacement has common features with Invasion Percolation in a Destabilizing Gradient. A phase diagram of fully developed drainage is then developed. The transition between stabilized displacement and fingering is controlled by the change of the sign of the gradient of the percolation probability, and the transition boundary is described by a scaling law involving the capillary number and the viscosity ratio. The theory is subsequently extended to correlated pore networks and a phase diagram involving the correlation length A is constructed. As the regimes of stabilized displacement are also those for which conventional theories (such as the Buckley-Leverett equation) apply, the phase diagram helps to delineate their validity.

P. 877
Implementation of Multirate Technique to Measure Relative Permeabilities Accounting
Authors: Virnovsky G.A. , Vatne K.O. , SkjaeveLand S.M. , Lohne A.
Published: December 2007

A practical implementation of the multi-rate steady-state technique to determine relative permeabilities from steady- state floods and its comparison with the standard steady-state technique is the main subject of the paper. The multi-rate technique is based on the theory of two-phase flow, and facilitates analytical corrections of relative permeabilities to account for capillary end effect. This is especially of practical importance if the experiment is performed at low rates when the relative role of capillary forces increases.

Normally, it is recommended to perform flooding experiments at high rates and/or on long cores to suppress capillary effects. Though this approach ensures simplicity in the interpretation procedure it disregards several factors one of which is that the relative permeabilities may depend on the rate. Proper account for capillary effects makes usage of long cores and high rates unnecessary.

A number of steady-state core floods have been performed at different rates varying from a high rate typically used in the lab experiments to a low rate approaching the range of typical reservoir rates. The experimental results, i.e. a set of relative permeabilities depending on the rate, have been interpreted both without and with account for capillary end effect. The previously developed analytical corrections for capillary effects were implemented in the interpretation. The results of analytical interpretation are quality controlled by numerical simulation of the experiments. It is shown that much of the difference observed in relative permeability curves and residual saturations measured at different rates can be explained by the influence of capillary end effect.

P. 901
Quantification of Vuggy Porosity in a Dolomite Reservoir from Borehole Images and Core, Dagger Draw Field, New Mexico
Authors: Hurley N. F. , Zimmermann R. A. , Pantoja D.
Published: December 2007

Vugs, which are large irregular pores, are a key pore type in many carbonate reservoirs. Because of coarse sample rate and limited vertical resolution, conventional wireline logs commonly mask vuggy porosity. This becomes a major problem when logging tools combine high vuggy porosity with low matrix porosity to derive average porosity values that fall below arbitrary commercial cutoffs. Non-completion of such zones commonly results in bypassed pay.

Borehole-imaging logs are high-resolution, oriented electronic "pictures" of the wellbore made by electrical or acoustic devices. Pixel-counting techniques, when applied to borehole images, can be used to detect and quantify vugs. The purpose of this study is to calibrate vugs quantified from borehole images to those quantified from digitally scanned core. Samples studied are vuggy dolomites of the Cisco and Canyon Formations (Pennsylvanian), Dagger Draw field, Eddy County, New Mexico. Results suggest that the neutron log is a good total-porosity device. However, this log suppresses the evidence for vuggy porosity which can lead to bypassed pay.
Determination of Oil/Water Saturation Functions of Chalk Core Plugs from Two-Phase Flow Experiments
Authors: Bech N. , Olsen Dan , Nielsen C. M.
Published: December 2007

A new procedure for obtaining saturation functions, i.e. capillary pressure and relative permeability, of tight core samples uses the pronounced end effect present in flooding experiments on such material. Commonly being a nuisance in core analysis, the end effect contains valuable information about the saturation functions. In core material with high capillary pressure, the end effect may allow determination of the saturation functions for a broad saturation interval. A complex core flooding scheme provides the fluid distributions and production data from which the saturation functions are computed by a least squares technique. An NMR technique is used for fluid distribution determination. The steady state situation at the end of a primary drainage experiment allows calculation of the drainage capillary pressure and the drainage relative oil permeability. The relative water permeability is calculated from the unsteady state data obtained during the transient part of this experiment. After a flow reversal, a new end effect develops at the opposite end of the core by an internal imbibition process, which at steady state allows calculation of the spontaneous imbibition capillary pressure and the imbibition relative oil permeability. Following a change from oil flooding to water flooding, the forced imbibition capillary pressure is calculated from transient pressure drop measurements. An undesirable interdependency of the saturation functions is avoided by their calculation from different data sets. Killough's method is employed to account for the scanning effect in hysteresis situations for both capillary pressure and relative permeability. The scanning parameter is determined as well. The procedure is demonstrated on chalk samples from the North Sea. The experimental time is intermediate between the centrifuge and porous plate methods. The procedure is superior to the centrifuge and mercury injection methods respectively by eliminating errors from end effects and using reservoir relevant fluids.
Revealing the Petrophysical Properties of a Thin-Bedded Rock in a Norwegian Sea Reservoir by the Use of Logs, Core, and Miniperm Data
Authors: Flolo Lars Helge , Menard Wendell P. , Weissenburger Ken W. , Kjaerefjord Jostein M. , Arnesen Dag M.
Published: December 2007

An unconventional thin-bed analysis based on logs, core and miniperm data was needed to calculate the petrophysical properties of a reservoir under development in the Norwegian Sea. More than half of the reservoir section under investigation is composed of heterolithic facies: thinly interbedded sandstone and mudstone layers from one to several centimeters in thickness and of variable quality. By using miniperm measurements with 1-cm spacing on slabbed core, it was possible to resolve the properties of the rock far below the vertical resolution of conventional wireline logs and relate them to the bulk log measurements,

P. 815