bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Model to Describe Formation Damage During Particle Movement and Deposition in Porous Media
Authors: Moghadasi J. , Sharif A. , Kalantari-Dahaghi A. M. , Motaie E.
Published: December 2007

Several investigators have studied formation damage due to invasion of solid suspensions and some modeling approaches have also been reported in the literature, most notably the application of effective medium theory and percolation theory in two and three-dimensional capillary networks. This paper presents a new model, which is based on mass balance transfer function of particles flowing through the porous media. The linear forms of the model are described as well as the radial forms. Although the differential equations derived are similar to the general form of diffusion-convection equations, the marked difference is the suitability of the model, for being applied for variation of parameters, such as particle concentration in the fluid, injection rate, density of solid particles, against the depth and time of invasion. This transfer function is solved by MATLAB program (Version 5.3.2) and SliMULINK software. The results of the simulation run agree reasonably well with the experimental damage data obtained in laboratory.
Using High-Frequency Downhole Vibration Technology to Enhance through-Tubing Fishing and Workover Operations
Authors: Joppe L. C. , Mackenzie G. , McGurk M.
Published: December 2007

In coiled tubing conveyed through-tubing fishing operations, conventional jarring technology often creates limitations due to the requirement to repeatedly cycle the coiled tubing over the gooseneck in order to actuate and re-cock the jar. It is well known and documented in our industry that this repeated cycling leads to pipe fatigue and coiled tubing life reduction. Additionally, the low frequency, high-impact of the jarring assembly, may in some cases cause the fish to become wedged tighter.

Vibratory and high frequency impact tools have been found to provide operational and economic benefits over hydraulic, time delayed jarring tools in a variety of through tubing fishing and workover applications, particularly in horizontal and extended-reach wells.

As opposed to jars, vibratory type impact systems are capable of delivering significant impact forces at the fish with only limited set-down weight or over pull available making them particularly well suited to the constraints of coiled tubing operations. These hydraulically powered systems are configured to deliver downward impacts in compression and upward impacts in tension. Both downward and upward impacts are achieved without the necessity to cycle the coiled tubing between impacts, therefore significantly reducing low-cycle pipe fatigue. Additionally, when a fish is stuck in sand or debris, temporarily suspending or liquefying sand particles by lighter high frequency blows as delivered by an impact tool while over pull is applied offers a higher degree of success in freeing the fish.

This paper will outline the uses and advantages of down-hole high-frequency vibration technology from a coiled tubing perspective and also describe the development and laboratory testing results of a new, modular vibratory impact tool offering a significantly reduced operating length yet delivering greater impact thus increasing the operating envelope for such tools adding demonstrable value to a variety of coiled tubing fishing and workover operations.
Gas Hydrates and Deepwater Operation: Predicting the Hydrate-Free Zone
Authors: Mohammadi A. H. , Tohidi B.
Published: December 2007

The application of extended subsea networks and transportation of unprocessed well-streams are amongst favorable options for reducing field development and operational costs. These pipelines normally convey a cocktail of multiphase fluids, including mixed electrolyte produced water and liquid and gaseous hydrocarbons and may therefore be prone to hydrate formation, which potentially can block the pipe and lead to serious operational problems. For deep water operation, even saturated saline solutions may not provide the required protection, unless combined with chemical inhibitor. The reported data on hydrate formation in mixed salt and chemical inhibitor are very limited and in some cases inconsistent.

In this work, a model is introduced to predict the hydrate free zone in mixed salt and chemical inhibitor designed for offshore and deep water applications. The model is based on combination of the Valderrama modification of the Patel-Teja equation of state with non-density dependent mixing rules and a modification of a Debye-Hückel electrostatic term, which is applied to systems containing salt and chemical inhibitor by correcting the properties of the aqueous phase such as dielectric constant, density and molecular weight. A linear mixing rule is used for determining the dielectric constant of salt-free mixture by introducing an interaction parameter (in dielectric constant mixing rule), which is tuned using the freezing point data of aqueous solutions containing salt and organic inhibitor. The binary interaction parameter between salt and organic inhibitor is adjusted using water vapor pressure data in the presence of salt and organic inhibitor. The predictions are compared with experimental data and a literature model, demonstrating the reliability of the developed model.
Sweep Improvement Options for the Daqing Oil Field
Authors: Wang D. , Han P. , Shao Z. , Chen J. , Seright R. S.
Published: December 2007

This paper investigates the potential of various approaches for improving sweep in parts of the Daqing Oil Field that have been EOR targets. Possibilities included (1) gel treatments that are directed at channeling through fractures, (2) colloidal dispersion gels, (3) reduced polymer degradation, (4) more viscous polymer solutions, and (5) foams and other methods. Our studies indicated that the polymer flood should have provided excellent sweep throughout the vast majority of the patterns under consideration. However, since ASP flooding is being considered to increase recovery efficiency from the Daqing Oil Field, mobility control and sweep improvement will be especially important and challenging during implementation of any future ASP process.

Fractures were present in a number of Daqing wells (both injectors and producers). Because the fractures were narrow far from the wellbore, severe channeling did not occur. On the contrary, fractures near the wellbore aided reservoir sweep. These near-wellbore fractures substantially increased the injectivity index during injection of polymer solutions and increased oil productivity index in the production wells. These observations may be valuable during implementation of future floods where very low-mobility chemical (i.e., ASP) banks must be injected to maintain mobility control.

Several modes of polymer degradation were considered, with mechanical (shear) degradation being of most concern. Appropriate use of near-wellbore fractures may effectively mitigate mechanical degradation, as well as improving injectivity.

Several new polymers show potential for cost-effective improvements at Daqing. Increased polymer concentration was also considered. A number of other approaches are (or have been) under investigation, including colloidal dispersion gels, foams, ASP foams, steam, microbes, and polymer solutions prepared with reduced salinity.
Compressible Streamlines and Three-Phase History Matching
Authors: Cheng H. , Oyerinde D. , Datta-Gupta A. , Milliken W.
Published: December 2007

Reconciling high-resolution geologic models to field production history is still by far the most time-consuming aspect of the workflow for both geoscientists and engineers. Recently streamline-based assisted and automatic history matching techniques have shown great potential in this regard and several field applications have demonstrated the feasibility of the approach. However, most of these applications have been limited to two-phase water-oil flow under incompressible or slightly compressible conditions.

We propose an approach to history matching three-phase flow using a novel compressible streamline formulation and streamline-derived analytic sensitivities. First, we utilize a generalized streamline model to account for compressible flow by introducing an ‘effective density’ of total fluids along streamlines. This density term rigorously captures changes in fluid volumes with pressure and is easily traced along streamlines. A density-dependent source term in the saturation equation further accounts for the pressure effects during saturation calculations along streamlines. Our approach preserves the 1-D nature of the saturation equation and all the associated advantages of the streamline approach with only minor modifications to existing streamline models. Second, we analytically compute parameter sensitivities that define the relationship between the reservoir properties and the production response, viz. water-cut and gas-oil ratio (GOR). These sensitivities are an integral part of history matching and streamline models permit efficient computation of these sensitivities through a single flow simulation. Finally, for history matching we use a generalized travel-time inversion that has been shown to be robust because of its quasi-linear properties and converges in only a few iterations. The approach is very fast and avoids much of the subjective judgments and time-consuming trial-and-errors inherent in manual history matching.

We demonstrate the power and utility of our approach using both synthetic and field-scale examples. The synthetic case is used to validate our method. It entails the joint integration of water cut and gas oil ratios from a 9-spot pattern in reconstructing a reference permeability field. The field-scale example is a modified version of the ninth SPE comparative study and consists of 25 producers, 1 injector and aquifer influx. Starting with a prior geologic model, we integrate water-cut and GOR history via the generalized travel time inversion. Our approach takes only a few hours on a PC for the entire history matching while preserving the geologic continuity.
Experimental Evaluation of the Blockage Efficiency of a Novel Gel System To Mitigate Water-Cut Problem of Producing Wells
Authors: Amanullah M.
Published: December 2007

Water production is a problem of paramount importance from technical, environmental and oil production points of views. The processing, treatment and disposal of produced water cost millions of dollars for a single field. On the other hand, high water production causes a drastic reduction in oil production. The issue of excessive water production has been addressed by the industry by placing different gel system in the reservoir to block the water flow and facilitate the oil flow. The most commonly used solutions are polymer gels with chromium (Cr3+) as the cross-linking agents in the gel system. Some of the polymer gel systems are not effective at temperature above 70 °C due to the thermal and hydrolytic degradation of the polymer. Moreover, the precipitation of the toxic cross-linking agent with increased temperature and pH is a major environmental concern.

This paper describes the water blocking efficiency of an environment friendly and biodegradable gel system to mitigate the water cut problem of producing wells. The newly designed gel system has no cross-linking agent and is stable up to 194 °F (90 °C) temperature. The system is stable in the presence of divalent ions and also in a range of pH conditions. Experimental results indicate nearly 100% reduction in water permeability of 16/30 sand-pack after treatment. Flow test with mineral oil indicate higher oil permeability compared to water. However, oil permeability has been reduced dramatically compared to pre-treatment oil permeability. Hence, it is most suitable for treating the water zone of a reservoir.
More and More From Brownfields—A Structured Process To Deliver Value
Authors: Seong C. K. , Malek R. A.
Published: December 2007

Since 1996, PETRONAS has implemented a structured field development plan review process with its PS Contractors to maximize reserves and value from the brown fields. Even though every stage of the FDP Milestone Review has a clear objective and expectation, yet PMU and PS Contractors approach the review differently. Understanding the PS Contractors mindset is key to managing differing views. This paper will describe (i) PETRONAS roles and objectives as the national oil company – in relation to management of petroleum resources, (ii) the structured brown field development plan review process, in particular the four critical Milestone Review and its related key activities, (iii) observable differences between PMU and PS Contractors during each Milestone Review and some applicable rules used by PMU to manage the situation. As a result of this implementation, reserves addition have been realized, value created and cycle time for brown field development plan approval has reduced significantly. It should be noted that the structured field development plan review process is also applicable to the green field development, with some changes to the process.
Improved ASP Process Using Organic Alkali
Authors: Berger P. D. , Lee C. H.
Published: December 2007

This paper describes the use of a new type of organic alkali that replaces and improves upon traditional inorganic alkalis such as sodium hydroxide and sodium carbonate. The new organic alkali was evaluated in Alkaline Surfactant Polymer (ASP) formulations containing commonly used surfactants and polymers. The effect of organic alkali on IFT, adsorption and viscosity was compared to that of a conventional inorganic alkali in these formulations. The organic alkali was found to be compatible with brines containing high TDS and high divalent cation concentrations. They can be used in brines without the need for softening and in some cases they provide better results than conventional alkali in systems where either can be used. The organic alkalis have the advantage of improved compatibility with unsoftened brines, surfactants and polymers. Their non-toxic, biodegradable properties make them particularly suitable for environmentally sensitive applications such as offshore and inland lakes.
How Far Can a State-of-the-Art NPV Model Take You in Decision Making?
Authors: Pedersen F. B. , Hanssen T. H. , Aasheim T. I.
Published: December 2007

The mature North Sea hydrocarbon province is often referred to as a guiding star, indicating changes the E&P industry soon will experience in other parts of the world. A number of the recent North Sea development concept decisions have ranked high in complexity. Most of these fields have so far been regarded as sub-economic. The recent oil price increase has sparked renewed interest, but the underlying risks are unchanged. Complex and interdependent risks in reservoirs and fluid regimes, unclear third-party options, CAPEX and OPEX risks, schedule risks and costs of rectifying equipment failure all constitute challenges to finding the optimal concept selection.

This complexity is relatively easily integrated in a full probabilistic economic model, yielding powerful inputs to concept ranking, design debottlenecking and illumination of the needs for flexible development plans and inbuilt excess capacities. However, such models will add most value within a risk-based decision making framework, with clearly defined decision criteria and identification of the key external risk factors.

In this paper we take a look at good practices for concept definition, qualitative screening and NPV ranking, focusing in particular on a risk-based decision framework. We discuss how soft issues in many cases set aside the recommendation from the quantitative model and finally look into the need for better communication between modellers and decision makers.
Wellbore Stability Assessment for Highly Inclined Wells Using Limited Rock-Mechanics Data
Authors: Simangunsong R. A. , Villatoro J. J. , Davis A. K.
Published: December 2007

Assessment of wellbore stability involves several parameters for which data that may not be readily available. The rock mechanics input data required for analysis are complicated and costly to acquire. Nevertheless, wellbore stability assessment plays an important role in the design of drilling and production of oil and gas wells; therefore, a methodology for bridging the data gap is needed.

This paper presents a methodology for wellbore stability assessment with limited data, using common reservoir data. The methodology provides correlations for estimating in-situ stress regimes based on the regional data and rock mechanics parameters based on its lithology. Afterwards, in-situ stress and rock mechanics parameters are used to investigate the effect of stress anisotropy on the mechanical stability of the borehole for various inclination angles.

Three failure criteria are reviewed to assess borehole stability, namely Mohr-Coulomb, Drucker-Prager, and modified Lade criteria. These failure criteria are combined with linear and isotropic rock mechanics behavior.

Evaluation of stress behavior of a variety of rock lithologies was performed, using failure criteria. Results indicate that the modified Lade criteria tend to be more realistic than the Mohr-Coulomb and Drucker-Prager criteria for these evaluations. Furthermore, this study confirms that, for any type of rock, an increase in borehole inclination angle increases the risk of borehole instability. Sensitivity analysis, based on various reservoir parameters, is performed and confirms the reliability of the correlations reviewed.

The methodology presented here can be used as an indicator of borehole instability risk before drilling. Subsequently, the results can be used to optimize drilling design and enhance safety in drilling operations.
Simulation of Experimental Gas-Recycling Experiments in Fractured Gas/Condensate Reservoirs
Authors: Shadizadeh S. R. , Rashtchian D. , Moradi S.
Published: December 2007

Gas recycling experiments were conducted on a gas condensate sample in a fractured model. Experimental Model was then numerically simulated with compositional simulator. The objectives were to investigate effects of gas recycling on condensate recovery from a naturally fractured reservoir under complete pressure maintenance process.

In laboratory scale we could accurately analyse behavior of in-place and injected gas in fracture and matrix blocks and understand how the production mechanisms affect ultimate recovery in this reservoir model. In reservoir scale, due to high heterogeneity and lack of required data such an accurate investigation is impossible.

In the simulated model after history matching of cumulative gas and condensate production and composition variation history of produced gas, some sensitivity analysis were performed. Simulation results show that gas recycling increases liquid recovery more than 2.5 times for the reservoir if the fracture model behaves as dual permeability fractured reservoir. If model behavior supposed to be dual porosity, condensate recovery decreases dramatically due to early break through of injected gas via fractures. Cyclic injection-production and decreasing the production rate are the factors directing the process to higher ultimate recoveries. Nitrogen injection effect has also been established showing less recovery than dry gas injection case.

Finally, lacks of data for a complete compositional simulation of such models are mentioned. If the data be prepared prior to performing the experiment, results could be up-scaled to the reservoir with higher degree of assurance.
First Through-Tubing Gravel-Pack Recompletion Performed in Japan
Authors: Numasawa M. , Salahudin S. , Hashimoto H. , Choy C. Y. , Mitsuda S.
Published: December 2007

Japan Petroleum Exploration Co., Ltd (JAPEX) and Mitsubishi Gas Chemical Company Inc. (MGC) operate the Higashi Niigata Oil & Gas Field in Niigata, Japan. One of the wells, NS-6, a gas producer, had produced a large amount of formation sand, which filled up the surface production facility and production tubing resulting in production being shut-in at the end of 2002.

This paper will discuss a workover performed on this well, which was conducted in an effort to extend well life. Due to the depleted nature of the reservoir, a through-tubing gravel pack was chosen as the means to re-complete the well. The through-tubing gravel pack service was supplied by a local service company working in co-operation with a specialist through-tubing service provider who also provided onsite installation supervision. This method of through-tubing remediation was the first time this type of installation was used in Japan.

The local service company personnel with support from their Malaysia sand-control team worked with the customer and the specialist through-tubing service provider to design the job, and as a result of their expertise, the job was successfully performed. This case history will discuss 1) the planning and successful execution of the job, 2) its cost efficiency and safety, 3) its capability to meet majority of JAPEX’s and MGC’s goals, and 4) the valuable experience it provided for planning future remedial activities that may be required in this field.
Optimization of Conformance Decisions Using a New Well-Intervention Simulator
Authors: Ansah J. , Soliman M. Y. , Ali S. , Moreno C. , Jorquera R. , Warren J.
Published: December 2007

For many years, operators and service companies have applied conformance treatments without adequate methods to verify treatment efficiency, since complexities of the treatment and reservoir systems have made attempts to quantify the effects of these conformance solutions with available tools unreliable. A comprehensive database had been developed with help of several operating companies of conformance treatments that were performed by several service companies over 30+ years. This database shows that in the absence of proper diagnostics and analysis, the success of a conformance treatment usually hovers around 50% even in well established areas. Application in new areas usually fares significantly worse, with a success ratio of 30% or less.

An important reason for this unacceptable situation is the tendency to design a conformance treatment without adequately considering reservoir effect. In this paper, we present a methodology and a numerical simulation approach that are aimed at improving the success ratio of conformance treatments.

Optimum conformance treatments must consider: placement techniques,treatment size,reservoir temperature and pressure effects, andtracking of conformance fluid-property changes with time and temperature.

To adequately design a conformance treatment, it is important to predict both pressure and temperature profiles inside the wellbore and the reservoir. Using a numerical simulator that couples the wellbore with the reservoir provides a very efficient means for developing a methodology to optimize conformance treatments. Simulated examples are given to shed insight into basic conformance phenomena such as coning and channeling. Most importantly, two field cases are presented to demonstrate practical application of the developed methodology for designing an optimum conformance solution.

This new methodology reduces operational and economic risks associated with conformance treatments. It also allows for optimization of these treatments through more accurate prediction of water and hydrocarbon production.
The Effect of Sulfur Deposition on Gas Deliverability
Authors: Mei H. , Zhang M. , Yang X.
Published: December 2007

Sour gas reservoirs with high content of sulfur are distributed widely around the world. Solid elemental sulfur which dissolves in the gas phase originally in the reservoir, may deposit when the thermodynamic conditions of the temperature, pressure or composition changes in the process of production. Deposition of solid elemental sulfur may block the pores in the formation and significantly affect the gas deliverability. In this paper, sulfur deposition mechanism is analyzed in the reservoirs. Based on the characteristics of sulfur deposition in the formation, a corrected function is introduced to modify the gas flow. Then, an evaluation method of the effect of sulfur deposition on gas deliverability is presented. For a practical sour gas reservoir, the gas deliverability considering sulfur deposition in formation is calculated and evaluated. The results show that the decrease degree of gas deliverability is different and it depends on the physical parameters in the formation on which the gas well is located.
Numerical Analysis of a New Stochastic Bubble Population Foam Model
Authors: Zitha P. L. J. , Du D. -X. , Uijttenhout M. G. H. , Nguyen Q. P.
Published: December 2007

Foam flow in porous media plays an important role in oil and gas recovery. Besides experimental studies, the prediction of foam behavior in the applications relies on macroscopic modeling. In this paper, we present a numerical analysis of foam flow in porous media using a new stochastic bubble population (SBP) model. We also present a sensitivity analysis to the main parameters. The idea that foam flow in porous media can be described as a stochastic process emerged from recent studies of foam flow through porous media using X-ray computed tomography (CT). The model is simple as it describes the bubble generation using mainly two parameters, the maximum bubble density and a foam generation constant. It is also robust because it grasps the essence of foam physics in homogeneous porous media. A good qualitatively agreement exists between the numerical predictions and the water saturation profiles obtained from the CT scan experiments.
Comparison of Secondary and Tertiary Recovery with Change in Injection Brine Composition for Crude Oil/Sandstone Combinations
Authors: Zhang Y. , Morrow N. R.
Published: December 2007

Numerous examples of dependency of waterflood efficiency on brine composition have been observed for sandstones. Improved oil recovery depends on complex crude oil/brine/rock (COBR) interactions. Elucidation of the circumstances and mechanisms of increased oil recovery still requires extensive laboratory testing. Special attention is being given in laboratory and pilot tests to increased recovery by injection of low salinity brine in both secondary and tertiary modes. Investigation of connate brine composition as a key variable has been extended to variation in initial water saturation (Swi). Mixed-wettability (MXW) cores were prepared by aging with crude oil at reservoir temperature for a range of initial water saturations.

Oil recovery as % original oil in place (OOIP) generally increased with initial water saturation for secondary recovery by injection of low salinity brine. CS crude oil/Berea sandstone combinations were essentially insensitive to displacement with low salinity brine in secondary mode even when the injection pressure was double that for oil recovery by injection of reservoir brine (RB). However, significant increase in tertiary mode (about 6% OOIP) was observed for the same COBR combination when low salinity brine was injected after establishing residual oil by injection of reservoir brine.

Low salinity brine floods with Minnelusa oil and 400 md Berea sandstone showed more than 13% OOIP increase in recovery over that given by flooding with reservoir brine. For the Minnelusa oil, however, very little additional oil was produced in tertiary mode. From available data, response to injection of low salinity brine in tertiary mode was clearly highest for reservoir rock and crude oil. Overall, rock properties are the most important factor in improved recovery by injection of low salinity brine.
Effect of Oil Viscosity on Heavy-Oil/Water Relative Permeability Curves
Authors: Wang J. , Dong M. , Asghari K.
Published: December 2007

For heavy oil reservoirs, the oil viscosity usually varies dramatically during production processes, such as thermal process or solvent injection. This paper presents an investigation of the effect of oil viscosity on relative permeability curves for heavy oil-water systems. Unsteady-state displacement tests were conducted in sandpacks under a typical injection flow rate in a heavy oil recovery process. A series of crude oils with a wide range of viscosities were used in the measurements. Large pore volumes of water were injected to minimize the errors caused by the extrapolation of the recovery data. History matching was used to obtain the relative permeability curves, in which capillary pressure was included. It was found that, for the same injection flow rate, heavy oil-water relative permeability curves systematically shifted with oil viscosity. With increasing oil viscosity, the residual oil saturation increased and the oil and water relative permeabilities decreased at the higher water saturation range. Irreducible water saturation tended to decrease with increasing oil viscosity. Micromodel experiments were conducted to visually investigate the difference in the flow behaviour between heavy oil-water and light oil-water systems. Interacting capillary bundle models were used to analyze the impact of oil viscosity on the residual oil saturation. This work aids in the laboratory measurement and determination of the representative relative permeability curves for heavy oil-water systems, as well as in the proper use of relative permeability curves in reservoir simulation for heavy oil development.
Reducing the Permeability of Sandstone Porous Media to Water and CO2: Application of Bovine Carbonic Anhydrase Enzyme
Authors: Asghari K. , Mirjafari P. , Mahinpey N. , Dong M.
Published: December 2007

This paper presents the results of an investigation on the application of the enzyme bovine carbonic anhydrase for reducing the permeability of a sandstone porous medium during CO2 flooding. This process provides a method for improving conformance of injected water and CO2 in an absolutely environmentally friendly manner. Carbonic anhydrase enzyme accelerates the hydration reaction of CO2 with water. Hence, in presence of carbon dioxide and divalent ions, such as calcium, this enzyme leads to rapid precipitation of calcium carbonate. The precipitation reaction causes reduction in the permeability of the flooded regions of the reservoir. Therefore, upon subsequent injection of CO2 and water, injected fluids would flow through the unswept parts of reservoir, improving the conformance of the injected CO2 and water.

Experiments were carried out to investigate the effect of various enzyme concentrations, temperature and pH on the precipitation reaction. Enzyme concentrations at 2, 4 and 8 micro mole per litter were tested. Also, effect of temperature was studied by performing experiments at room temperature, 30 °C and 55 °C. A mathematical model was developed to predict the extent of precipitation of calcium carbonate. Subsequently, coreflood experiments, using Berea sandstone cores, were conducted and the degree of reduction in the permeability of the cores was measured. Also, in order to investigate the effect of injection scheme on permeability reduction, two different methods of injection were tested. For all sets of flow experiments, the permeability of the core was reduced to less than half of its initial value.
Evaluation of Acid Precursor-Enzyme System for Filter-Cake Removal by a Single-Stage Treatment
Authors: Siddiqui M. A. , Al-Anazi H. A. , Al-Ansari A. A. , Bataweel M. A. , Hembling D. E.
Published: December 2007

Water based drill-in fluids usually contain starch and xanthan polymers and sized calcium carbonate particles, which help in developing an effective filter cake during drilling process to control fluid loss. Proper removal of the drill-in fluid filter cake from the pay zone is essential to maximize productivity. The latest technique for filter cake clean-up is the application of acid and enzymes in a single stage. The prime advantage of this technique is the uniform placement of acid through precursor in long horizontal wells. Other benefits include: cost and time saving by avoiding multistage treatment and reduced risk of tools corrosion, which is associated with mineral acids.

A detailed study was conducted to evaluate the efficiency of acid-precursor-enzyme system to be used in multi-lateral, maximum reservoir contact wells. The evaluation was performed by using samples of polymer based drill-in fluids and dry bulk of sized calcium carbonate in terms of return permeability determination, change in particle size distribution, and weight loss.

Results indicated that the generated acid mainly targeted fine particles of calcium carbonate present in drill-in fluids and dry bulk. This paper presents results of lab investigations and merits (or demerits) of single stage treatments.
Performance Prediction of a Rich Gas/Condensate Reservoir Through Material Balance and PVT Behavior: A Case Study
Authors: Zeidouni M. , Movazi G. H. , Pourghasem B.
Published: December 2007

With a 217 STB/MMSCF liquid-gas ratio (LGR) Sarvak reservoir of CARBONATE field in Iran is one of the richest gas condensate reservoirs in the world. Due to asphaltene precipitation during well shut-in, it is impossible to acquire static pressure data for the reservoir. Since the reservoir pressure is of the main reservoir parameters for performance prediction, material balance calculations was performed based on volumetric and PVT data to determine current reservoir pressure. Furthermore the retrograde condensate deposition (liquid drop-out) is also calculated with the introduction of new parameter of Liquid-Fluid ratio (LFR).

The curve of P/z (the ratio of pressure and gas deviation factor) versus cumulative gas production is conventionally utilized to predict the gas reservoir performance. This method is used for gas condensate reservoirs by replacing gas z-factor with two-phase z-factor (zT). Since reservoir pressure data are not available a direct usage of the above method for CARBONATE-Sarvak reservoir is impossible. As such the experimental data of Constant Volume Depletion (CVD) experiment have been used that simulate the gas condensate fluid behavior. The experimental data are simulated using the PVT simulator of Winprop and tuned to Peng-Robinson EOS to provide non-available parameters and to check the validity of the data. Gas deviation factor at the dew point (zd) was determined as 1.2433 based on which the two-phase z-factor was calculated for different pressures below the dew point pressure. Backward calculation was performed to correct the available experimental data of produced gas percentage to reservoir conditions. The percentage of gas produced to reach the dew point was determined as 3.3029 percent of the Gas Initially In Place (GIIP). Utilizing the GIIP of 620 MMMSCF concluded from volumetric calculations the reservoir will reach the dew point after 20.48MMMSCF of gas production. It is estimated that current reservoir pressure after cumulative gas production (Gp) of 60 MMMSCF would be 5819 Psia. Furthermore the retrograde liquid deposition of the reservoir is determined to be 35.31 MMSTB through the plot of liquid-Feed Ratio (LFR) versus Gp/G.
Determination of Capillary Pressure and Relative Permeability From Spontaneous- Imbibition Data in Gas/Liquid/Rock
Authors: Jia F. , Zhou K. , Li K.
Published: December 2007

Capillary pressure and relative permeability are important parameters in reservoir engineering. Techniques frequently used to measure capillary pressure and relative permeability simultaneously are complicated and time-consuming. On the other hand, it is also difficult to measure the two parameters in low permeability rocks. It would be useful if capillary pressure and relative permeability could be inferred from spontaneous imbibition tests. This is because such tests are relatively simple, fast, and economical. In the present study, an analytical approach was developed to determine capillary pressure and relative permeability simultaneously by using experimental data of spontaneous water imbibition into gas- saturated rock. Spontaneous water imbibition tests in different rocks were conducted to test the proposed approach. Both capillary pressure and relative permeability were calculated using the proposed approach and the results were closely equal to those measured using different methods.
Analysis and Interpretation of Interwell Connectivity From Production and Injection Rate Fluctuations Using a Capacitance Model
Authors: Yousef A. A. , Lake L. W. , Jensen J. L.
Published: December 2007

This paper presents new applications of a capacitance model to characterize reservoirs based on temporal fluctuations in injection and production rates. In a previous report (SPE 95322), two coefficients are determined for each injector-producer pair; one parameter, λ, quantifies the connectivity and another, τ, quantifies the fluid storage in the interwell region. This report describes the development of this method into a diagnostic tool to enhance inference about preferential transmissibility trends and the presence of flow barriers.

Applying the capacitance model to results from numerical flow simulation, we found that complex geological conditions are often not easily identified using λ and τ values separately. However, combining them in certain representations enhances the inference about geological features. Two different representations are used: one representation is a log-log plot of the λ's versus the τ's for a producer and nearby injectors, and another representation is the flow capacity plot where the λ's and the τ's are combined as in Lorenz plots. These techniques were tested using a numerical simulator and then applied to data sets from the South Wasson Clearfork and the North Buck Draw fields.

The simulation results and field applications show that the relation between λ's and corresponding τ's are consistent with the known heterogeneity, the distance between wells, and their relative positions. The flow capacity plots and the log-log plots are capable of identifying whether the connectivity of an injector-producer well pair is through fractures, a high-permeability layer, multiple-layers or through partially completed wells. Finally, the approach, based on Lorenz plots, can make use of the extensive literature already available on the interpretation of such plots.
Molecular Characterization of 6 Unrelated Italian Patients With 5α‐Reductase Type 2 Deficiency
Authors: Baldinotti F. , Majore S. , Fogli A. , Marrocco G. , Ghirri P. , Vuerich M. , Tumini S. , Boscherini B. , Vetri M. , Scommegna S. , Rinaldi R. , Simi P. , Grammatico P.
Published: December 2007

ABSTRACT: Steroid 5α‐reductase (5αR) deficiency (OMIM number #264600) is a rare 46,XY disorder of sex differentiation caused by mutations in the 5αR type 2 gene (SRD5A2) resulting in dihydrotestosterone deficiency during fetal development. We report on the analysis of the SRD5A2 gene in 6 unrelated 46,XY Italian patients with external genitalia morphology ranging from predominantly female to nearly completely male. Three subjects were seen and assessed at birth, 1 patient was referred to us before puberty, and 2 at postpubertal age. Six different causative mutations (5 missense and 1 nonsense) and a rare polymorphism were identified. Four patients presented homozygous single‐base substitutions. These SRD5A2 mutations were located in exon 2 (variant Cys133Gly), exon 4 (Gly196Ser and Ala207Asp) and exon 5 (Tyr235Phe). A fifth subject was a compound heterozygote who carried a nonsense mutation in exon 1 (Trp53X) and a second SRD5A2 alteration in exon 5 (Tyr235Phe). The final patient presented a mutation in only 1 allele (Gly34Trp) together with the Ala49Thr variant. The molecular characterization of these patients made it possible to identify novel mutations and to confirm, before gender assignment or any surgical approach, the suspected 5αR deficiency in 2 newborns, 1 of whom had inconclusive hormonal data. 5αR deficiency in subjects without parental consanguinity and the presence of compound heterozygotic patients suggest that SRD5A2 mutations carrier frequency may be higher than previously thought.
A Dose‐Response Study of Testosterone on Sexual Dysfunction and Features of the Metabolic Syndrome Using Testosterone Gel and Parenteral Testosterone Undecanoate
Authors: Saad Farid , Gooren Louis J. , Haider Ahmad , Yassin Aksam
Published: December 2007

ABSTRACT: The objective of this study was to observe the dose‐response effects of testosterone (T) treatment on symptoms of sexual dysfunction and the metabolic syndrome. Two cohorts of elderly men with late‐onset hypogonadism were followed over 9 months. Group 1, consisting of 28 men (mean age, 61 years; mean T level, 2.07 ± 0.50 ng/mL), received long‐acting T undecanoate (TU; 1000 mg); group 2, composed of 27 men (mean age, 60 years; mean T level, 2.24 ± 0.41 ng/mL), received T gel (50 mg/day) for 9 months. In patients treated with T gel, plasma T levels rose from 2.24 ± 0.41 to 2.95 ± 0.52 (statistically significant) at 3 months, 3.49 ± 0.89 (statistically significant) at 6 months, and 3.80 ± 0.73 ng/mL at 9 months (T level at 6 months was compared with T level at 3 months). With TU, plasma T levels rose from 2.08 ± 0.56 to 4.81 ± 0.83 (statistically significant) at 3 months, 5.29 ± 0.91 at 6 months, and 5.40 ± 0.77 ng/mL at 9 months. With TU, the plasma T levels were statistically significantly higher than with T gel With TU, there was a greater improvement in sexual symptoms and in symptoms of the metabolic syndrome. With both treatments, changes in waist circumference correlated with changes in total, low‐density, and high‐density lipoprotein cholesterol. Parameters of safety were not different between the 2 treatments. T administration had a beneficial effect on sexual dysfunction and symptoms of the metabolic syndrome in elderly men. The higher plasma levels of T generated with TU than with T gel were clearly more effective, indicating that there is a T dose‐effect relationship.
Morphology and Meiotic Segregation in Spermatozoa From Men of Proven Fertility
Authors: Collodel Giulia , Moretti Elena
Published: December 2007

ABSTRACT: Estimates of semen parameters are important for defining normal ranges, which are currently established by 1999 World Health Organization guidelines. However, it is well known that semen evaluation is questionable because it is necessary for only 1 sperm to be able to reach and fertilize the oocyte. Spermiogram parameters and sperm morphology, evaluated by transmission electron microscopy (TEM), were performed on semen samples from 25 men of proven fertility. Despite a generally normal sperm concentration, progressive motility was reduced in 9 cases. Sperm characteristics were evaluated with an established technique, and the mean of the percentages of sperm pathologies were confirmed by comparing to previous reports. A comparison of apoptosis and necrosis in the samples, as detected by TEM and an annexin V/propidium iodide assay, was also performed. Fluorescence in situ hybridization was carried out on the same samples using probes for chromosomes 18, X, and Y. The mean value of the frequency of total aneuploidy in the analyzed group was 0.627% (25th percentile = 0.563%; median = 0.625%; 75th percentile = 0.690%). This study of the incidence of disomy and diploidy in spermatozoa from fertile, apparently normal individuals is important for making comparisons with infertile cohorts to determine the real increase of aneuploidy in those cohorts.
Exposure of Juvenile Rats to the Phytoestrogen Daidzein Impairs Erectile Function in a Dose‐Related Manner in Adulthood
Authors: Pan Lianjun , Xia Xinyi , Feng Yao , Jiang Chunxia , Cui Yingxia , Huang Yufeng
Published: December 2007

ABSTRACT: Health benefits of isoflavones such as genistein and daidzein have led to an increasing interest in consuming soybeans or soy‐containing food. However, possible adverse effects of such plant estrogens on the male reproductive system, particularly penile erection, have not been sufficiently evaluated. In previous research, we observed that exposure of adult rats to daidzein could attenuate apomorphine‐induced erections. To identify the impact of daidzein exposure in early life on erectile function, we evaluated erectile capacity using an apomorphine‐induced erectile test and determining intracavernous pressure after exposure of juvenile rats to daidzein at a dose of 2, 20, or 100 mg/kg for 90 days. Meanwhile, the levels of sex hormones, including testosterone, luteinizing hormone, and follicle‐stimulating hormone, were determined. Both subtypes of the estrogen receptor (α and β) in the corpora cavernosa were also detected immunohistochemically. When the rats were examined at adulthood, we observed that those animals treated with a medium (20 mg/kg) or high (100 mg/kg) dose of daidzein, but not with a low dose (2 mg/kg), showed lower plasma testosterone levels and attenuated erectile parameters, including apomorphine‐induced erections and intracavernous pressure concomitant with markedly decreased expression of estrogen receptor β in the corpora cavernosa. However, the penis still grew to its normal size, as in controls. Thus, these results suggested that exposure of juvenile rats to daidzein in a relatively large amount could adversely affect penile erection in adulthood.
Higher Sperm DNA Damage in Semen From Men With Spinal Cord Injuries Compared With Controls
Authors: Brackett Nancy L. , Ibrahim Emad , Grotas Jason A. , Aballa Teodoro C. , Lynne Charles M.
Published: December 2007

ABSTRACT: Semen from men with spinal cord injuries (SCI) and control subjects was investigated for sperm DNA damage using the sperm chromatin structure assay. Three experiments were performed. In experiment 1, the DNA fragmentation index (DFI) was compared in semen from SCI subjects and control subjects. In experiment 2, the % DFI was determined in repeated ejaculations to examine the effect of anejaculation on DFI. In experiment 3, the DFI was determined in neat vs processed semen to examine the effect of necrospermia or leukocytospermia on DFI. The results of experiment 1 showed a significantly higher mean (± SEM) DFI in the semen of SCI subjects (65.2% ± 6.6%; range, 42.3%–90.8%) compared with control subjects (15.4% ± 2.9%; range, 5.4%–33.5%; P < .001). In experiment 2, there was a high correlation between the DFIs obtained in the first semen specimens and the DFIs obtained 3 days later in semen of the same SCI subjects (rs = .94; P < .02). In experiment 3, the results showed no significant difference between mean DFI in aliquots of neat semen (79.3% ± 9.9%) vs matched aliquots of semen processed to remove dead sperm and leukocytes in SCI subjects (75.2% ± 16.1%). The DFI is higher in semen from men with SCI vs controls. The cause of this condition is unknown but does not seem to be due to prolonged anejaculation or to the proximate conditions of necrospermia or leukocytospermia. The relevance of these findings to fertility outcomes with SCI male partners remains to be determined.
Technical Writing in English Renaissance Shipwrightery: Breaching the Shoals of Orality
Authors: Tebeaux Elizabeth
Published: December 2007

Describing the emergence of the first shipbuilding texts, particularly those in English provides another chapter in the story of the emergence of English technical writing. Shipwrightery texts did not appear in English until the middle decades of the seventeenth century because shipwrightery was a closed discourse community which shared knowledge via oral transmission. The shift from orality to textuality in shipwrightery did not occur until advancing navigation principles enabled ships to sail in open waters. Shipping rapidly became a commercial business, and shipwrightery was forced to move from closely-guarded simple design principles to mathematically-based designs too complex to be retained only in memory of shipwrights and shared via oral transmission. Textual transmission began to supplant oral instruction. The evolution of English shipwrightery provides rich research opportunities for historians tracking the development of technical writing.