bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of Mechanisms and Procedures for Producing Favourable Shapes of Hydraulic Fractures
Authors: Cleary Michael P. 
Published: December 2007

ABSTRACT
The paper identifies some primary features of tectonic conditions, rock response and fluid rheology which can strongly affect the shape evolution of hydraulic fractures in representative reservoir formations. Numerous mechanisms are described, with emphasis on the question of fracture containment within regions of desirable transmissivity increase. Relevant natural characteristics include: contrasts of in situ stress, variations in material deformabi1ity/fractur-ability, and differences in permeability between pay-zones and adjacent strata. Various degrees of crack-arrest are possible but the dominant component of most mechanisms is the retardation of fracture growth caused by impedance to fluid flow. Artificial biasing of flow patterns may be achieved, by chemical or mechanical preparation of the region to be stimulated and by use of complex frac-fluid rheology. Implementation of these phenomena in practical designs typically requires detailed analysis with numerical models, but numerous recommendations can be made to improve conventional practises: for instance, fracturing pressures must be carefully limited, pretreatment can be helpful and rheology/proppant-scheduling can be exploited to much greater extents.
Electromagnetic Propagation Tool (EPT): Comparison of Log Derived and in Situ oil Saturations in Shaly Fresh Water Sands
Authors: Freedman R. , Montague D. R. 
Published: December 2007

ABSTRACT
We have examined log and laboratory data on cores and/or sidewall samples from three Shell wells producing heavy crude oil from shaly sands containing fresh water of variable and unknown Rw. Using only downhole data from the EPT and a porosity tool we have derived oil saturations SOEPT and compared them with in situ saturations So inferred from laboratory and log data. Although the deviations of SOEPT from So exhibit a great deal of scatter, the results nevertheless demonstrate that one can identify the oil-bearing zones in this difficult log interpretation environment. The results are especially encouraging when one considers that values of SOEPT were obtained from a minimum log suite (specifically SP, EPT and density) without knowing the water resistivities, Rw, the cation exchange capacities, Qv, of the sands and without any other auxiliary data not obtainable from downhole logs. A detailed description of the EPT tool and its resultant log is given in order to provide the log analyst with a useful and self-contained reference for this new logging tool.
History Match Simulation of Serrazzano Geothermal Reservoir
Authors: Pruess Karsten , Weres Oleh , Schroeder Ron , Marconcini Rodolfo , Neri Giuseppe 
Published: December 2007

Abstract
The simulator SHAFT79 of Lawrence Berkeley Laboratory has been applied to field-wide distributed parameter simulation of the vapor-dominated geothermal reservoir at Serrazzano, Italy. Using a three-dimensional geologically accurate mesh and detailed flow rate data from 19 producing wells, a period of 15.5 years (from 1959 to 1975) has been simulated. The reservoir model used is based on field measurements of temperatures and pressures, laboratory data for core samples, and available geological and hydrological information. The main parameters determined (adjusted) during development of the simulation are permeabilities and much of the initial conditions.
Simulated patterns of pressure decline show semi-quantitative agreement with field observations. Field pressures decline overall somewhat more rapidly than predicted in the simulation. It is concluded that (i) the interface between overlying steam cap and deeper boiling aquifer remains stationary during exploitation; (ii) the aquifer boils approximately uniformly throughout in response to production.
Furthermore, the simulation suggests that (iii) there is cold water recharge and/or incomplete heat transfer from the rock due to fractures in the margins of the reservoir, and (iv) some steam flowing to the main well field originates from deep fractures rather than from boiling in the two-phase zones modeled.
Simulation methodology and ambiguity of parameter determination is discussed.
Non-Darcy Flow in Dissolved Cas-Drive Reservoirs
Authors: Kadi K. S. 
Published: December 2007

ABSTRACT
Gas reservoirs have been simulated for turbulent (more appropriately visco-inertial) flow in the past. A study is extended to single-phase oil, and to two-phase non-Darcy flow in a solution-gas drive reservoir. The effects of normal sequence (increasing rate) and reverse sequence (decreasing rate) schedules, and the effects of liberation of gas on the Absolute Open Flow Potential (AOFP) and skin are considered. Analysis of the results obtained from the two-phase, one-dimensional radial model reveals that the oil non-Darcy pressure drawdown behaves like pressure drawdown in gas wells with turbulent flow. Formation flow capacity calculated from the constant rate drawdown test indicates that non-Darcy flow induces a skin which is rate dependent.
The performance of a depletion-drive reservoir obeying a non-Darcy type motion is compared to the performance of the same reservoir producing in a Darcy fashion. The pressure profile and the GOR curve are lower, and the gas saturation profile is higher for a given flowrate in the non-Darcy case in the range investigated. The non-Darcy AOFP is lower than the corresponding Darcy AOFP for a flow-after flow performance. Above the bubble point pressure, an increasing skin decreases the visco-inertial effects. When gas is present or is flowing, an increasing skin stabilizes the visco-inertial effects.
Application of Integrated Reservoir Analysis to Optimize Development Plan
Authors: Wang S. W. , Shivers B. , Setiawan Y. , Inaray J. , Harmawan I. , Fidra Y. 
Published: December 2007

Abstract
This work presents a methodology which uses nodal analysis, material balance, pressure transient analysis, and integrated production management (IPM) to determine reservoir boundary, original fluid in place (OFIP), and completion strategy for one of the reservoirs in West Seno field, the first deepwater development project in Indonesia.
The drainage area calculated from pressure test analysis compares favorably with that derived from seismic amplitude map. OFIP was used to (1) guide 3D simulation to study the potential of secondary recovery with water or gas injection and (2) build an IPM model to study optimal workover strategy.
Although reservoir size and OFIP were evaluated with various methods, the final results are very similar. This finding and successful history matching with IPM and 3D simulation models increase our confidence in the optimized development plan.
The Use of Vertical Seismic Profiles and Surface Seismic Profiles to Investigate the Distribution of Aquifers in the Madison Group and Red River Formation, Powder River Basin, Wyoming-Montana
Authors: Balch Alfred H. , Lee Myung W. , Miller John J. , Ryder Robert T. 
Published: December 2007

ABSTRACT
The water resource potential of deep aquifers (2,000 ft to 10,000 ft) such as the Madison-Red River interval in the Eastern Powder River Basin of Wyoming-Montana is of great importance to support the future heavy water demands that coal and other energy development activities will place on the limited known water resources of the area.
We have used conventional well data, vertical seismic profiles, and surface seismic reflection profiles to see whether porous, water-productive Madison-Red River sections can be distinguished from barren sections in advance of drilling.
Our observations suggest that porous productive end members are identifiable on the basis of acoustic differences, as observed on reflected wave trains in the exploration seismic frequency range.
Characterization of Sulphate Scaling Formation Damage From Laboratory Measurements (To Predict Well-Productivity Decline)
Authors: Bedrikovetsky P. G. , Moraes G. P. , Monteiro R. , Lopes R. P. , Rosário F. F. , Bezerra M. C. 
Published: December 2007

AbstractThe formation damage in scaled-up production wells caused by incompatibility of injected and formation waters have long been known. Precipitation of salts results in permeability decline. Among the most onerous of all scaling species is that of sulphates, particularly barium and strontium sulphates.We study effects of porous media on the BaSO4 scaling kinetics.A new methodology for determination of reaction rate coefficient from coreflood tests consists of the sequence of diffusivity reaction free tests, of transient tests with chemical reaction, and of simultaneous injections of both injected and formation waters with quasi steady state concentration profiles for barium and sulphate ions. The diffusivity tests serve for dispersivity coefficient determination. Quasi steady state tests allow determination of the reaction rate coefficient versus velocity. The transient test data as compared with the mathematical modelling data validate the model and the data of steady state test data treatment.An analytical model developed is used for treatment of quasi steady state test data. The transient tests are treated by a numerical model.The main result of the work is proportionality between the reaction rate coefficient and flow velocity for the parameter range studied.
Experimental Design as a Framework for Multiple Realisation History Matching: F6 Further Development Studies
Authors: Alessio L. , Coca S. , Bourdon L. 
Published: December 2007

AbstractHistory matching is traditionally complex and time-consuming: multiple parameters influence the match and their inter-dependency produces effects that are difficult to predict. Defining the match itself can be challenging, since various indexes or responses can be used: water breakthrough timing, pressures, layer contributions etc… Consequently, whilst multiple realisations methodologies are routinely applied for "green" field development planning, most of the time incremental activity screening on "brown" fields is done on a single matching realisation -"the" matched model - with little confidence that the full range of uncertainties is captured.Experimental design provides a well-suited framework to tackle the challenge of multi-realisation history matching, following these key steps:Selection of key parameters with variance analysis, Reduction of dimensionality by creating hybrid parameters, using techniques related to principle component analysis, Predicting matching domains: combination of parameters levels (once discretised) that are likely to generate a match. This greatly helps the likelihood of finding multiple matching realisations, covering the range of parameter variation.This methodology was successfully applied in the F6 subsurface studies, aimed at screening field redevelopment opportunities. F6 is the largest gas field in the Central Luconia carbonate province, offshore Sarawak (Borneo), having a GIIP of more than 7 Tscf. With over half the reserves produced, well capacity is now threatened by the rising aquifer. In order to safeguard and possibly increase the reserves, a field review was undertaken to identify further development opportunities, and a multi-realisation approach was chosen to capture the effect of key subsurface uncertainties on those activities.A total of 28 matching realisations were generated, covering the variation range of the identified key seven parameters whilst optimising the number of runs performed, thus saving time. Key to the success of the method lies in the integration of disciplines to allow the upfront identification of parameters and their ranges.The screening of redevelopment options against those realisations allowed to establish the range of expected incremental reserves, assess risks, and form a sound basis for business decisions.
The Impact of Condensate Blockage and Completion Fluids on Gas Productivity in Gas-Condensate Reservoirs
Authors: Al-Anazi H. A. , Solares J. R. , Al-Faifi M. G. 
Published: December 2007

AbstractCoreflood experiments were conducted on carbonate and sandstone cores from gas-condensate reservoirs in Saudi Arabia to assess the loss in gas relative permeability caused by condensate accumulation and water blockage. Field samples of condensate were used in these experiments to mimic two-phase flow around the wellbore region when the bottom hole flowing pressure dropped below the dewpoint. The impact of several fluids used as completion fluids was also investigated at reservoir conditions. Several solvents were evaluated to remove both condensate and water blockages.Experimental results show that reductions of 70% to 95% in gas relative permeability were seen in reservoir cores due to condensate blockage. The studied solvents were found to be effective for enhancing gas relative permeability. This study also quantified the required methanol treatment volumes to increase gas relative permeability at lab conditions, which could be extrapolated to field conditions. The reduction in gas relative permeability was more pronounced during two-phase flow in the presence of water saturation due to the dual effect of condensate and water blockage. Methanol displaces retrograde condensate and maintains improved gas relative permeability well into the post-treatment production period.Methanol-water mixtures were ineffective in removing condensate blockage and decreased gas productivity after their treatment. Methanol was effective in removing water from the cores. A mixture of isopropyl alcohol and methanol yielded similar favorable results as pure methanol. In summary, the evaluated solvents were all effective in removing condensate blockage from the core, delayed condensate accumulation, and enhanced gas productivity.
An Empirical Correlation to Predict Diamond Bit Drilling Rates
Authors: Duklet Clare P. , Bates Thomas R. 
Published: December 2007

ABSTRACT
Diamond bit drilling tests have been performed at the Drilling Research Laboratory (DRL) in Salt Laie City, Utah. These tests were sponsored and supervised by the Shell Development Company. The tests simulated down hole drilling pressures on a typical diamond drill bit and oilfield formation. Variations of typical field operating variables were tested for penetration rate response. An empirical equation has been derived from the test results to predict diamond bit drilling rates.
Fiber Optics Used To Support Reservoir Temperature Surveillance in Duri Steamflood
Authors: Nath D. K. 
Published: December 2007

Abstract
In thermal fields, temperature profiles usually are acquired as part of a sound reservoir surveillance plan to manage heat in the ground. The conventional method used to acquire a temperature profile is to run a wireline log across the interval of interest, usually through tubing or casing in observation wells.
In Duri Steam Flood (DSF) production wells, it is not possible to run conventional temperature logs in producers without pulling out tubing pumps due to the complexity of the completion. One alternative to the real-time temperature profile in DSF producers is to use an optical fiber enclosed inside a steel tube strapped onto the outside of the tubing string and passed through the tubing hanger and top flange at the wellhead. The tubing hanger must be modified to accommodate the pre-installed fiber-tube installation.
The survey will collect temperature data that can be used to determine the temperature and extent of a steam chest and the temperature gradient in both overburden and under-burden. This information is necessary to set steam injection target rates using the Vogel and Neumann methodologies. The data are also useful in mitigating steam breakthroughs and eruptions, and to identify bypassed oil.
Gas Condensate Damage in Hydraulically Fractured Wells
Authors: Ravari R. R. , Wattenbarger R. A. , Ibrahim M. 
Published: December 2007

Abstract
The work in this paper is a result of a problem encountered in producing a low permeability formation from a hydraulically fractured well in South Texas. The well was producing from a tight gas condensate reservoir and there was concern about damaging the well if the wellbore pressure fell below the dew point. However, it turned out that condensate damage was not a problem. Lower wellbore pressures only resulted in higher rates.
This study used compositional reservoir simulation to model production for three situations; all having low permeability and hydraulic fractures. The simulation results verify what was observed in the field: lower wellbore pressure yields higher production rates. Although some condensate damage was observed below the dew point, none of the cases showed that lower wellbore pressures led to worse overall well performance. Even for the case of a very rich gas condensate, the optimum conditions correspond to the lowest pwf.
The results of this research may be a step forward in improving the management of gas condensate reservoirs by understanding the mechanics of liquid build-up. Although some wells may be "ruined" by low wellbore pressures, this was not evident in the cases in our work. The hydraulic fracturing seemed to reduce the condensate damage effect.
Understanding Corrosivity of Weighted Acids
Authors: Ke M. , Boles J. , Lant K. E. 
Published: December 2007

AbstractAcids are frequently used to treat wells and remove formation damage during completions or in subsequent workovers. Sometimes, to prevent gas intrusion, excessive co-mingling of fluids and fluid density segregation, or to maintain hydrostatic pressure, a weighted acid will be applied to ensure successful treatment. Weighted acids are normally prepared by mixing acid with halide salts or concentrated halide brines such as sodium chloride (NaCl), calcium chloride (CaCl2), sodium bromide (NaBr), calcium bromide (CaBr2), or a combination of zinc bromide and calcium bromide (ZnBr2/CaBr2), etc. Selection of salts or brines is primarily based on the required properties of weighted acids and cost effectiveness. There are many publications related to corrosion and inhibition in acids; however, regarding corrosion behavior of weighted acids on tubular materials, relatively little information has been published.Extensive laboratory testing was conducted to evaluate corrosivity of weighted acids prepared with different brines. Corrosion data is presented which indicates that depending on the brine applied, a weighted acid system may produce much higher corrosion rates over the same strength of acid prepared with fresh water (regular acid). When applied in weighted acids, some corrosion inhibitors or inhibitor packages qualified for regular acids do not provide adequate corrosion protection on regular oilfield tubulars. Also presented are evaluations of the weighted acids with regard to compatibility and effectiveness of the acids to maintain their strength and dissolution properties.
A Constitutive Equation for Nonlinear Stress-Strain Curves in Rocks and its Application to Stress Analysis Around a Borehole During Drilling
Authors: Morita Nobuo , Gray K. E. 
Published: December 2007

ABSTRACT
The stress-strain behavior of Berea, Ohio, and Pecos sandstone was measured intensively under triaxial loading paths. Both compression and extension tests were performed at different pore fluid pressures. These tests showed that four modes can arise in the stress-strain curves up to failure: an initial nonlinear portion; linear portion; a final nonlinear portion; and volume change of the rock maxtrix due to pore fluid pressure. The characteristics of these modes were studied, and a nonlinear model was developed to represent the important characteristics, i.e., the four modes, of the behavior of sandstones by means of a constitutive equation in such a way as to satisfy certain mathematical requirements.
A finite element model using nonlinear stress-strain relationship was developed which simulates the stress state of a structure up to failure. The finite element model was used to predict fracture pressure around a borehole during drilling. The shape of the borehole is either circular or elliptic, and the tectonic stress is directional. Since the nonlinear stress state depends upon loading history, the loads were applied incrementally, simulating phenomena occuring during the drilling process. It is shown that use of conventional linear stress-strain behavior gives significantly erroneous results for well stability problems.
The Development of an Optimal Artificial Neural Network Model for Estimating Initial, Irreducible Water Saturation – Australian Reservoirs
Authors: Goda H. M. , Maier H. R. , Behrenbruch P. 
Published: December 2007

Abstract
Initial, irreducuble water saturation, Swir is an important parameter that needs to be determined accurately when attempting to characterize hydrocarbon reservoirs. Swir is also one of the key parameters in relative permeability relationships. Furthermore, an unrepresentative value of Swir may lead to invalid residual oil saturation estimates when the latter is correlated with the former.
Swi may have a dependence on several other parameters, including: absolute rock permeability, porosity, pore size distribution and capillary pressure. The above parameters are directly influenced by geological deposition and subsequent changes, such as diagenesis effects (for example clay-filled pores). It is a common practice to measure Swir utilizing representative core plugs by measuring capillary pressure with a centrifuge, at speeds equivalent to the maximum representative (reservoir) capillary pressure. However, a semi-empirical model that could estimate Swir to a good degree of accuracy would be of significant value.
Over the last few years, artificial neural networks have found their application in petroleum engineering. In some cases such models have outperformed models employing conventional statistical and regression analysis. In this study, an Artificial Neural Network (ANN) model has been developed for the prediction of Swi (specifically irreducible saturation, Swir) using data from a number of onshore and offshore Australian hydrocarbon basins. The paper outlines a methodology for developing ANN models and the results obtained indicate that the ANN model developed is successful in predicating values of Swir over the range of data used for calibration. This neural network based model is believed to be unique for Australian reservoirs