bluuebunny/crossref_metadata_2025 huggingface dataset:
Intelligent Wells: Horizontal Well Simulation for Thin Oil Rims Abundant in the Niger-Delta - A Case Study
Authors: Mogbo Obuekwe
Published: July 2010

A simulation case study is described which illustrates the application of an intelligent horizontal well to an isolated reservoir with a thin oil rim in the Niger Delta.

Simulation of the intelligent well ability to simultaneously monitor and respond to reservoir conditions in two or more zones has proved to be a challenge for the performance forecasting of such wells. Recently, in the Niger Delta, Intelligent wells have began to be routinely used both for their economic benefit and their advantages in accessing remote and difficult locations for work-over during hydrocarbon exploitation. Furthermore, intelligent horizontal wells are finding utilization because remote thin oil rims are abundant in the Niger Delta.

The paper begins by a brief discussion of the intelligent well simulation methodology: Several fitting chokes (ICVs) are modelled along the length of the well in a commercially available simulator. This means that production from different segments could be controlled individually by the ICV's. The effect of the smart completion is recognised and analysed: constraints of water and gas production rates per segments are applied to shut in well segments automatically as water and gas constraints are reached. Furthermore, typical economic analysis for intelligent well justification is done. The results show that intelligent horizontal well completion is justified for this field.
Parametric Study of Condensate Buildup in a Naturally Fractured Gas Condensate Reservoir
Authors: Ebrahimi M.
Published: July 2010

The main difficulty usually encountered in gas-condensate reservoirs is the loss of valuable condensed liquid in the reservoir due to capillary forces, a phenomenon called condensate blockage. The presence of condensates when coupled with the complexity of fluid flow in fractured reservoirs can increasingly obscure the expected performance of such reservoirs. A thorough understanding of the factors leading to condensate buildup in fractured reservoirs is crucial for deciding a proper strategy to exploit such reservoirs. In this paper, a compositional model is used to predict and physically justify the single-well performance of a naturally fractured gas-condensate reservoir having different reservoir properties and production schemes.

The current study reveals the important role of capillary pressure in trapping condensates, especially in highly fractured reservoirs where the effect of gravity drainage is minimized. Higher matrix block sizes can reduce the amount of trapped liquid. However, high critical condensate saturation can dampen the effect to some extent. Pore size uniformity is another important factor that causes less condensate buildup due to less capillary pressure. Higher production rates result in earlier condensate dropout peak. The peak is lower for higher rates, a phenomenon attributed to velocity stripping. Furthermore, the effect of gas and liquid diffusion is the most crucial in tighter matrices and can significantly reduce the trapped condensates.
DC Electric Standalone Choke
Authors: Abicht Daniel
Published: July 2010

With the successful installation, commissioning, and operation of the first All Electric System in the Dutch Sector of the North Sea, the All-Electric Subsea Controls Systems technology continues to prove its advantages. As the 2-off subsea trees are currently gaining field experience, proving their defined targets such as e.g. improved reliability & availability and real time feedback, spin-off technology already has been developed.

Considering a customer survey and subsequent market analysis the need for an electric high precision choke being controlled from a standard electro-hydraulic multiplexed Subsea Control Module (SCM) clearly has been identified. A mature development initiative planting the design on the successfully field proven CameronDC™ Choke was initiated.

The DC electric Standalone Choke can be controlled from an electro-hydraulic multiplexed SCM utilizing minimum power consumption along with a standardized CANopen interface enabling high precision choke control, continuous position feedback, and improved operatability. In combination with dedicated Choke Control Software flow from multiple wells for enhanced recovery can be optimized.

Along with the description of the experience gained during the development this paper will discuss the inherent advantages of the DC electric Standalone Choke applied to subsea production systems.
The Occurrence of Unconventional Natural Gas Reservoirs Offshore Trinidad
Authors: Figueira B. , De Silva J. M. , DeLandro-Clarke W-L. , Bertrand W.
Published: July 2010

The island of Trinidad, situated at the easternmost extremity of the Eastern Venezuela Basin, is a known producer of conventional hydrocarbons, oil in previous years and natural gas at present. However, not much work has been done to identify, and more importantly, quantify the unconventional natural gas hydrate resource present in the Trinidad area. This paper presents a methodology for the identification of natural gas hydrate in Trinidad and the initial findings of this methodology using primarily three-dimensional (3D) seismic data from eastern offshore. The dataset covered an area of approximately 1788.6 km2 of transition zone between the continental shelf and slope in the Columbus Basin.

Analysis of the data shows the presence of several positive indicators which suggest that natural gas hydrate is present in the oceanic sediments. Bottom simulating reflectors (BSRs) were observed on the seismic data and the areal extent of these BSRs was determined to be 516.8 km2 or approximately 29% of the area of the mapped seafloor. Several mud volcanoes were also observed on the seismic volume.
Identifying and Quantifying Thin-Bedded Pay (Part A): Log Characteristics and Reservoir Quality
Authors: Henderson K. , Rose H. , Winter R.
Published: July 2010

Thinly bedded reservoirs are common throughout the Columbus Basin, but have traditionally been overlooked as productive targets. The presence of interbedded shales suppresses resistivity values within the thin sand beds (<2 feet thick), resulting in low-resistivity log signatures that do not meet conventional pay cut-offs. Core data and advanced high-resolution log analysis are required to accurately evaluate reservoir quality. In the absence of such data, thin bedded pay can still be identified on conventional logs as low resistivity intervals and a modified petrophysics workflow can be used to estimate gas-in-place.

An example is taken from a recently drilled well where 180 feet of conventional core was acquired together with an advanced logging suite over a thinly bedded interval. The resulting petrophysical analysis indicates lower water saturation than predicted by conventional logs, which is independently supported by wellsite plug measurement. Core data also demonstrates that the porosity and permeability distributions in the cleaner, thin sand beds show similar ranges to conventional "thickly bedded" sands, irrespective of bed thickness. Porosity and permeability decrease in the more heterolithic zones (with increasing silt content) as would be expected.

These results endorse the concept that reservoir quality of thin sands is comparable to that of thicker sands, although this may not be evident from conventional log analysis. As a result, a well-by-well screening was carried out for a number of fields in the Columbus Basin to identify and classify potential thin bedded intervals based on typical log signatures. The reservoir properties of these intervals can then be evaluated using a modified petrophysics approach based on calibration to the core and advanced logging technology. This workflow has proved to be an important tool for the identification of thin bedded intervals, highlighting opportunities for targeted surveillance and providing an inventory of potential targets for future access.
Identifying and Quantifying Thin-Bedded Pay, Part B: The Use of Dynamic Data to Evaluate Productivity Potential in Gas Reservoirs
Authors: Baillie K. , James-Romano J.
Published: July 2010

Intervals of thinly bedded sands have been identified above or below conventional ‘thickly bedded’ gas reservoirs currently under production. The level of contribution to flow from thin bedded pay however is uncertain and difficult to distinguish from that of the thick, conventional pay intervals. Production data solely from these intervals is extremely limited, so confirming production and ultimate recovery from these resources is challenging.

Thinly bedded intervals have historically not been targeted for completion, but may still be contributing to gas rates over a long term production time scale. Producing reservoirs in the bpTT portfolio may already provide evidence for the potential productivity of thin bed pay. Static pressure data from several wells in reservoirs with thin bed pay above or below completed conventional pay intervals have suggested pressure support from a lower rate source when wells are shut in for an extended period of time. Pressure transient analyses in other wells have interpreted heterogeneities in reservoirs where traditionally only conventional thick bedded intervals were considered.

In lieu of direct evidence of production such as Production Logs and costly dedicated Thin Bedded Pay well tests, existing data has been used to confirm contribution to flow from thin bed pay and add to recoverable volumes. Formation pressures for a reservoir in the Amherstia field were used to prove depletion and increase the recoverable volumes from time bed pay in 2009. This interval was consequently identified as a future recompletion opportunity. Thin bed pay intervals were also targeted and completed in two newly drilled wells in the Cashima field. Though still early in their production lives, these wells are already showing signs of contribution from thin bed pay. The Amherstia and Cashima success stories demonstrate the potential for thin bed pay as an important resource for the future of bpTT.
Ensemble Based Characterization and History Matching of Naturally Fractured Tight/Shale Gas Reservoirs
Authors: Ghods Parham , Zhang Dongxiao
Published: July 2010

Tight sand and shale gas reservoirs are becoming bigger players in natural gas supply system as easily developed gas resources become scarcer, natural gas prices go higher, and more efficient technologies become available to develop these hard-to-access reservoirs. Although these reservoirs are hard to develop, recent technologies such as better hydraulic fracturing are making them more productive.

Production and development of these types of reservoirs depend heavily on the hydraulic fracturing and the existence of natural fractures in the formations. Since the permeability of the matrix is very low no commercially feasible gas production can be achieved without fracturing. Therefore, characterizing and understanding the fractures have become of great importance.

We have proposed using a combination of methodologies for fracture characterization and simulation in tight gas reservoirs. Dual Porosity Dual Permeability modeling has been used for simulating fractured reservoirs. For a commercial simulator to be able to simulate the fluid flow in a reservoir, properties such as permeability and porosity should be known which are, however, not adequately measured. The most readily available measurements are indirect observations such as bottom-hole pressures and production rates. Using indirect measurements to constrain the model parameters requires solving an inverse problem. In this study, Ensemble Kalman Filter (EnKF) is used for the estimation purposes. EnKF is a Monte Carlo based, minimum mean square error (MMSE) estimation tool that generates multiple realizations based on the prior knowledge of the reservoir, in which the model performance is improved via sequential assimilation of the observations.

Our proposed methodology is tested on several synthetic 2D reservoir models containing a number of fractures, some intersecting the wells. The results have proven the applicability and the advantage of this methodology. We have shown that EnKF can be used efficiently to characterize a fractured reservoir when the approximate orientation of the fractures is known which may be obtained from the stress-strain field data in the reservoir.
Implementation of PinPoint Fracturing Technique in the Western Egypt Desert
Authors: Mohsen Adel , Ali Mohamed Ahmed , Samiee Rady Abdel , Ibrahim Ehab , Taha Islam Mohamed , Hamdy Mostafa
Published: July 2010

In the western desert region of Egypt, previous propped multiple-fracture treatments were performed using conventional methods (i.e., perforate, frac, set mechanical/zone isolation, and repeat cycle). Although the resulting treatment efficiency was satisfactory, other methods were being considered to help reduce cost and improve production performance. Also, it was desired to decrease total operational time, which would further impact economics (rig time, production delay, etc).

In an attempt to improve production response, fracturing designs in the El Fadl field in the western desert went from a standard three-stage design up to as much as a six-stage design to more effectively stimulate the pay zones. A careful review of the field and operations suggested possible benefits from implementing the pinpoint method for hydraulic-fracturing treatments. It was, however, not a simple case of just applying a hydraulic-fracturing treatment to every potential zone, but required proper well screening, thorough log analysis, calculating and validating mechanical rock properties, and enhanced 3D fracture modeling to achieve a successful campaign.

A pinpoint method for stimulation was implemented to perform multistage jobs at reduced costs. As the stage count per well was increased, production response and economics were improved. Both treatment design and staging design with this fracturing technique continue to be further refined as performance and statistical analysis of previous design changes are completed.

This paper discusses a pinpoint method for frac treatment and the methodology applied on a recent well. Differences in job execution that will be discussed include: using a hydrajet perforating mechanism instead of conventional casing-gun perforation, time-consumption reduction, analysis of vertical-fracture coverage per potential zone, and cumulative production response from the different designs tested. This could serve as guidelines for other operators who might be facing similar challenges in the North Africa region and elsewhere.
How to Integrate Wireline Formation Tester, Logs, Core and Well Test Data to Get Hydraulic Flow Unit Permeability’s: Application to Algeria Gas Field
Authors: Elarouci Fethi , Mokrani Nabil , El Djoudi Salim Mouici , Hill Peter
Published: July 2010

Reservoirs in Algeria typically contain multiple rock types from different facies depositional systems, and their identification and their evaluation in some areas, is becoming more challenging.

It’s not easy to get a unique permeability value for specific flow-unit without combining different formation evaluation disciplines. Logs, cores and Well tests data, provide information not only of different kinds of permeability but also at different scale measurements.

The presented methodology is a case study of an integrated work performed during an exploration and appraisal stage in a gas field in Algeria.

The integration technique steps consisted of:

Identifying facies and hydraulic units from core data analysis Computing permeability curve in the entire reservoir including the non-cored zones by combining logs and porosity/permeability relationship of each hydraulic flow unit. Analyzing well testing transient pressures and estimating flow capacity. Computing permeability at the identified flow-unit scale by the analysis of wireline formation tester data using its inflatable straddle packer configuration.

The synthetic permeability curve showed a good correlation between core data and predicted values. A thickness that is actively contributing to the flow has been identified. Permeability values at the flow-unit scale were then computed.

The obtained results from the integrated technique provide accurate dynamic characteristics in a gas-bearing formation and constrain the producibility knowledge of a reservoir.
Testing and History Matching ES-SAGD (Using Hexane)
Authors: Ayodele Oluropo Rufus , Nasr Tawfik N. , Ivory John , Beaulieu Gilles , Heck Gord
Published: July 2010

For the first time, we present in public domain, experimental and history-matched results of 2D scaled laboratory testing of ES-SAGD with hexane as the co-injected solvent. Experimental results of ES-SAGD (with hexane) were also compared with the equivalent SAGD. The 2 experiments, which were conducted at the Alberta Research Council's Thermal Gravity laboratory, are 2-D high pressure/high temperature experiments and were conducted at 2100 kPag +/− 50 kPag. The comparison of ES-SAGD and SAGD experiments shows that ES-SAGD using hexane performed better than an equivalent SAGD experiment. The energy consumption per unit oil recovered for ES-SAGD was lower than that of SAGD (11.5% less). The average oil recovery within the first 500 minutes (i.e. 11.3 years at field-scale) for the ES-SAGD process was also much higher (~10.93% higher). The ES-SAGD result was history-matched with a commercial reservoir simulator (CMG STARS). The history-matched ES-SAGD experiment gave satisfactory results in terms of oil production rates, cumulative oil production, and temperature distributions. The results presented in the paper provide data that can be scaled to field and assist in the design, optimization and parameter selection when ES-SAGD (with hexane or a pseudo-hexane solvents mixture) is considered as a recovery technology. Multi-pattern simulations based on history-matched data of a single well pair (pattern) show that multi-well pair (pattern) simulations can provide a suitable approximate analog for multi-pattern experiments, which can be scaled and used for planning and optimizing a pilot or a small-scale commercial project.
An Inequality-Constrained Extended Kalman Filter for Continual Forecasting of Interwell Connectivities in Waterfloods
Authors: Zhai Daoyuan , Mendel Jerry M.
Published: July 2010

Liu, et al [5], [6] developed an Extended Kalman Filter (EKF) for a producer-centric reservoir modeled as a collection of continuous-time impulse responses that convert injection rates of all contributing injectors into a production rate. Their EKF model estimates two parameters for each producer-injector pair, which can be used to compute an Injector-Producer-Relationship (IPR) value. Zhai, et al [18] then modified their EKF model to directly estimate the square-root of the IPR value for each producer-injector pair, and developed a set of heuristic strategies for implementing the EKF model on much more complicated and noisy real field-data. In both works, the IPR values of a whole field are obtained by the EKF processing of each producer model independently; however, an important type of injector-centric constraint needs to be imposed across producer-centric models, namely, the sum of the IPR values of each injector has to be less than or equal to one. Unfortunately, it is not possible to impose such constraints using the current EKF structure.

Recently, Simon, et al [12]-[14] and Yang and Blasch [16] have shown how to incorporate equality and inequality constraints into the structure of a Kalman filter. This paper extends their linearly constrained Kalman Filter to the producer-centric EKF model. For the first time, all of the producer-centric models are coupled together by constraint coupling due to the constraint on the sum of the IPRs. This paper then uses a mini-simulated oilfield to show how unconstrained EKF processing can cause the sum of the IPRs to be greater than one; and, demonstrates, using both simulated and real oilfield data, how the constrained EKF can be used to couple the whole field thereby obtaining the correct IPR values.
Unlocking Potential From a Marginal Clastic Field in Oman
Authors: Al-Harrasi A.. , Al-Salhi M.. , Rathore Y.. , Bareg S.. , Bhatti K.. , Shukaili S..
Published: July 2010

The remotely located Z field has no testing, processing or gathering facilities and production is currently processed at the closest field production station 20 km away. The Z field consists of multiple stacked Permian clastic reservoirs in a low relief three way dip-closed structure bounded to the east by a north northeast–south southwest trending fault. Few other faults exist in the field and the identified faults most likely act as baffles to flow. Hydrocarbons are trapped in the marginal marine Middle Gharif (MG3) reservoir unit and in the younger MG2 fluvial sand bodies. The fluid properties range from high gravity crude oil in the MG3 (45°API) to volatile oils in MG2. This high GOR fluid limited the artificial lift options. The initial reservoir pressure is 26 bar in the MG3 with a bubble point pressure of 22.2 bar.

Despite challenges and uncertainties, the Z field was successfully developed by an optimised IOR method utilising onsite waterflood development to maximise field NPV. Artificial lift options are continuously modelled to find the optimum lift mechanism (mix of free flowing and ESP wells). The field production stabilised since 20005 when water injection was implemented to avoid drawdown below bubble point.

Integrated field reviews and analysis lead to a better understanding of reservoir performance. The interference tests and transient analyses performed for both injectors and producers provided insight into the field performance. These reviews led to successful drilling in 2009 with an additional upside potential of doupling the field production.

The plan for this field is to further develop the MG3 with a water flood utilising streamline simulation and start the MG2 appraisal development since more well control points are now available.
Production Enhancement via Scale Removal in Nar Formation
Authors: Farrokhrouz M.. , Asef M. R.
Published: July 2010

High rate of gas production from a well may result in brine production from different formations. When incompatible brines with different degree of saturation are mixed, precipitation of the salt could plug the well. Evaluation of openhole section was performed on a well in a gas field in Iran to check the well productivity. Unexpectedly, the tool was blocked a few feet below the casing shoe indicating the reason for production reduction. Attempts to remove scale deposition were unsuccessful and motivated comprehensive review of potential reasons to identify the properties of precipitated mineral. Crystal overgrowth of sulfate salt was considered to be the most likely mechanism, because the production zone was located in Nar formation which was mainly composed of anhydrite.

A comprehensive investigation was conducted in order to verify the type of bridged section. In-situ chemical conditions were identified based on general geological data, rock formation, rock types and brine sampling in reservoir rock. In such case at each production rate a different volume of brine was observed. Therefore, aqueous environment, ions and other in-situ conditions were modeled. The model was constructed using dynamic simulation software. Based on this model salt precipitation was reproduced confirming in-situ scaling problem. A prototype was developed to disperse this material based on previous laboratory experiments. Quantity and volume of additives for well treatment and scale removal were calculated accordingly. A scheduled production plan was proposed to identify the potential problems and appropriate strategy at each production rate. Study of this case in terms of site investigation, problem definition, and solution identification could accumulate valuable knowledge to quickly solve the problems in similar cases. In addition, presented simulation method would be the most economical method for scaling prevention and production optimization.
Time-lapse Seismic Study of South China Sea
Authors: Yuhong Xie , Zhihong Chen , Jiaxiong Zhou , Aihua Gou , Yuecheng Sun , Weiwei Liu
Published: July 2010

Time-lapse seismic study of South China Sea was begun from 2001. Two time-lapse seismic projects(YC13-1 and DF1-1Gas Field) had been done before June 2009. The paper tries to introduce the success and lessons of these projects, which include project feasibility study, core measurement, data processing and integrated interpretation.
Associative Polymer Usage as Stimulation Diversion System for Multilayered Reservoirs: Case Study of its Effectiveness for Stimulating Tight Layers in Khuff Carbonate Formation from Saudi Arabia's Ghawar Field
Authors: Al-Harbi Abdulaziz , Al-Malki Bandar , Al-Haddad H.M. , Vielma Jose
Published: July 2010

Acid fracturing as stimulation treatment for lower permeability multilayered reservoirs has been extensively used for carbonate formations around the world. For multilayered reservoirs, the success of stimulation is highly dependent on the fracture capability to connect the layers, fluid leak-off, fracture geometry and stimulation fluid properties. In Khuff carbonate reservoir from Ghawar Field, the heterogeneous nature of the multilayered formation, temperature, layers separation and especially wellbore deviation along the interval to be stimulated present additional technical challenges for fracturing stimulation and all of them has been addressed by incorporating Associative Polymer blends as a separate step to assure an effective fracturing stimulation fluid diversion.

The paper will show a case study for gas well in Ghawar field where an effective diversion technique with Associative Polymers was used successfully in fracturing treatments which resulted in enhancing more of tight layers contribution and increased total productivity by more than an order of magnitude. Associative Polymer (AP) blended in an innovative way forming, a solids or fibers free non-reactive water base system. The new diversion system was successfully used in several gas wells completed in Khuff carbonate reservoir where clear diversion and acid reaction signatures have been implied by surface and bottom-hole pressure (BHP) data recorded during the entire treatments. Production increases in addition to Pressure Build-up (PBU) and Production Logging corroborated the flow contribution from all the perforated intervals included tight layers, which contrasts with offset producers previously treated with other types of diverting agents.

The paper will present for the first time the treatment design and benefits of AP blend diverting agent usage for acid fracturing stimulations. A case history where the wellbore orientation is 45 degree is going to be presented and discussed in detail. Field case shows that the wellbore deviation was not a limitation for the effective stimulation and for the AP blend system to work. In addition, this paper will provide some guidelines for potential use of this diverting agent and candidate selection, treatment design, and execution.
Tectonic Escape (Indentation) in Central Saudi Arabia, Possibility and Exploration Potential
Authors: Khalil Mesbah , Muzaiyen Emad , Hmoud Khalid , Ismail Luay
Published: July 2010

Tectonic analysis indicates a high possibility of tectonic escape (P. Tapponnier and others, 1982, Armijo, R and others, 1986) structures in central Saudi Arabia that could bear significant hydrocarbon exploration potential. This study aims to introduce a new tectonic model that explains several surface and subsurface newly mapped structures in central Saudi Arabia. Potential fields, seismic and surface geology data are integrated to accomplish this study.

Basement terrane analysis of the Arabian shield and its eastern continuation beneath the sedimentary basin indicates the general north-south orientation with differences in width and composition. It shows that the maximum crust thickness is in the middle of the outcropping shield with a promontory extending 200 km toward east in subsurface (Central Arabian Arch) where Triassic (Khuff) marine carbonates overlay the basement directly. The crust shows gradual thinning eastward from this promontory till the offshore Arabian Gulf. Some terranes show wedging-out and others show narrowing against the eastern side of the basement outcrops. This pattern suggests the tectonic escape of the wedging out and narrowing terranes against the competent Afif terrane since the InfraCambrian accretion of Arabia. The terrane accretion occurred by westerly driven terranes collided against the thick promontory of the Afif terrane causing dispersion toward south and north through east-west accommodation zones. Long segments of unusual east-west surface structures (faults and strike of strata) over the boundaries of the subsurface basement promontory from north and south are thought to be a dragging of the dispersed terrane fragments at the promontory boundaries. West of these east-west zones, deformation is concentrated at the north-south terranes with curved hard link transfer zones. This InfraCambrian tectonic setting is believed to have been reactivated during Phanerozoic tectonic phases to express its escape tectonics pattern further-up till outcrops. Re-distribution of the Phanerozoic stresses at that inherited basement fabric controlled the geometry of the sub-basins and their filling during extension phases. It controlled also the preferable locations of structural positive inversion during compression phases to form the fault related fold traps. This approach explains the diversity of structural styles in the sedimentary cover (compression, transpression, and transtension) that formed simultaneously during the Late Cretaceous compression but with different directions.
The Application of Precision Ultrasonic Technologies to Diagnose and Identify Crossflow between Formations, Flow behind Pipe and Casing Leaks
Authors: Zakaria Mahmoud , Al-Shehri Ayedh , Tammar Hassan
Published: July 2010

Investigating the integrity of a casing, with the tubing in place, has always presented a challenge to operators worldwide. Even more challenging, is taking on an investigation into cross flow between formations & identifying regions of flow behind pipe, all while the tubing is still in place.

Flow behind pipe has always been a well debated subject amongst industry professionals; most advancement in this matter has been subjective, based on well educated speculation and largely dependent on temperature profiles and changes in the geothermal gradient. Saudi Aramco have recently utilized a new ultrasonic based, diagnostic technology, in order to map regimes of flow behind pipe, identify cross flow between downhole formations, locate casing leaks with a pin-point accuracy, all while the tubing is in place, and while using conventional Electric Line logging.

This technology exploits the innate physical properties of ultrasound. The capacity of ultrasonic waves to propagate through numerous and varied media, including steel, liquids & compressed gas; allows a radial investigation of up to 3m. Unlike several technologies that utilize ultrasound, this diagnostic tool, is a passive listener, with no transmitters. It is designed to pick up the sonic energy fluctuations created by the turbulent flow of fluids over a specific spectrum within the ultrasound frequencies window. A window that is so uniquely suited for precision wellbore diagnostics.

This paper presents the basic physics behind the technology chosen by Saudi Aramco to address the aforementioned issues. It will highlight the possible applications of these tools and more specifically discuss the recent case studies successfully performed in Saudi Aramco.
A Comparative Study Between Empirical Correlations & Mechanistic Models of Vertical Multiphase Flow
Authors: Yahaya Anes Usman , Al Gahtani Abdallah
Published: July 2010

A number of empirical correlations and mechanistic models have been developed for predicting pressure drop and other fluid flow characteristics during multiphase flow in vertical wellbore. At any particular time, engineers are often faced with the difficulty of which particular empirical correlation or mechanistic model should be used to evaluate multiphase flow in vertical wellbore. This is because; a particular correlation or model may be developed under some certain assumptions or for a particular region which may not be applicable to other regions or under a new set of conditions.

This paper presents a study that was conducted to evaluate the predictive performance of both mechanistically based models and empirical correlations in calculating pressure drop and other flow characteristics in vertical multiphase flow. Using 414 real field data points covering pipe sizes of 2.375 in. to 7.0. in, oil flow rate of 280B/D to 23,200B/D, water cut up to 95%, gas-oil ratio up 927SCF/STB from the Middle East, the correlations and models are used to predict pressure drop in vertical multiphase phase flow for several wells. The predicted performance is then compared with actual measured well pressure drop data.

The empirical correlations evaluated are those conventional correlations of Hagerdon and Brown, Duns and Ros, Orkiszewski, and Beggs and Brill. While mechanistic models of Ansari et al, Aziz et al, Chokshi et al are also evaluated. The variations between the predicted and the measured are analyzed using statistical error analysis.

Based on the results from the analysis, mechanistic model of Ansari et al. out-perform all the conventional empirical correlations evaluated in this study for vertical multiphase flow for the Middle East region.
Moving the Immovable: Practical Offshore Appraisal Testing of Heavy and Sour Oil
Authors: Al-Ajaji Abdulaziz A. , Al-Nahdi Abdul Hakim , Gill Harmohan , Omidiya Abdur-Rasheed
Published: July 2010

Saudi Aramco has recently embarked on an exploration program targeted at evaluating potential heavy oil reserves, offshore Saudi Arabia's eastern coast. The oil being tested is classified as heavy oil with an API gravity as low as 10 degrees (field measurement). Appraisal well testing in an offshore setting of such low API oil is difficult, especially when environmental considerations are of outmost importance. The tests objectives were to obtain accurate reservoir parameters, collect representative reservoir samples, and dispose of all produced hydrocarbons (heavy oil) without adversely impacting (spill/ polluting) the offshore environment. Being offshore, with limited space availability on jack-up rigs, it was also crucial that the design of the test equipment and procedures take into account the potential presence of Hydrogen Sulfide (H2s).

This paper will present best practices, experience gained, and lessons learnt from appraisal well testing of heavy oil at offshore locations. Several offshore heavy oil well tests were successfully carried out, where all produced hydrocarbons were flared off without causing spills or polluting the sensitive marine environment.
Flow Simulation in Inflow Control Valves Using Lattice Boltzmann Modeling
Authors: Qahtani Abdullah M
Published: July 2010

Flow simulation in inflow control valves (ICVs) plays an important role in production optimization and control. The number of ICVs required for deployment as well as their configuration impact strongly on the production forecast and planning. Optimization of ICVs focuses mainly on minimal flow disruption and pressure loss to allow continuous flow through a designated section. In some applications computational fluid dynamics (CFD) was employed to simulate the flow inside the inflow devices. These computational efforts based on solving the Navier-Stokes equations, always are subject to the type of geometry simulated which requires tremendous meshing efforts and the adequate of flow models to capture the physics involved in a particular flow mode. Frequently, single phase flows are only modeled in ICVs to visualize the basics of the fluid paths, but still require computational artifices to simulate the flow. Since more than a decade, lattice Boltzmann (LB ) flow simulations have shown gradual strength as an alternative to CFD methods. Opposite to traditional methods such as finite differences, finite elements, finite volumes, the LB methods (LBMs) are mesh free and only require little formulation efforts to simulate a fluid flow. On the other hand, LBMs do not always present problems often met in traditional CFD method such as long computational times, poor convergence and numerical instabilities. LBMs are more efficient since they are based on rigorous description of transport phenomena via the Boltzmann equation. In the present work, a flow simulation of a generic ICV configuration is shown by the use of an LBM. Flow properties and velocity distributions are shown and discussed for different flow scenarios. Based on these results, further design optimization can be proposed to minimize undesired effects such as excessive shear and additional pressure drop.
Successful Exploitation of Khuff-B Low Permeability Gas Condensate Reservoir through Optimized Development Strategy
Authors: Rahim Zillur , Al-Anazi Hamoud , Al-Kanaan Adnan , Aziz Azly Abdul
Published: July 2010

Khuff-B and Khuff-C are the two carbonate reservoirs in the SA-1 field discovered in 1980 with the drilling of exploratory well SA-A. Production from Khuff-B began in December 1983 when a second well was drilled and both were put onstream. The development of Khuff-B was minimal until two years back and only nine stand-alone wells were exclusively completed in this reservoir at that time. Three of these nine wells were actually tied-in to the gas plant. Few other wells were combined Khuff-B/Khuff-C producers. In the commingled producers, Khuff-B’s contribution is significant only in areas where Khuff-C is of relatively poorer quality. The dominant production is generally from Khuff-C reservoir.

A large area is currently within Khuff-B reservoir boundaries with only few producing wells. The development of this vast area is required to meet the increased gas demand. Accurate evaluation of Khuff-B to ascertain reservoir potential and deliverability is of utmost importance. This paper evaluates the Khuff-B reservoir in the SA-1 field and proposes an optimal development plan to effectively deplete its reserves.

Based on detailed analyses, the Khuff-B area has been divided into three regions, namely AREA-1, AREA-2 and AREA-3: The good, moderate, and challenging low quality, tight reservoir. The average production rates from those areas vary between 5 and 50 MMSCFD. The optimal drilling plan in the low quality, low productivity area consists of identifying the productive layer through a slanted pilot hole followed by drilling an extended lateral to attain maximum reservoir contact. A second lateral can also be drilled in special cases where more than one developed layer is encountered in the pilot hole. This development approach also allows placing the production lateral much above the gas-water contact to avoid any future water production or influx. The strategy is promising, has already been implemented in the field, and the results have confirmed a high production, water-free gas rate from the Khuff-B interval.
Oxidative Stress in Rat Testis and Epididymis Under Intermittent Hypobaric Hypoxia: Protective Role of Ascorbate Supplementation
Authors: Farias Jorge Gonzalo , Puebla Mariela , Acevedo Alejandro , Tapia Pablo José , Gutierrez Eduardo , Zepeda Andrea , Calaf Gloria , Juantok Camila , Reyes Juan G.
Published: July 2010

ABSTRACT: Hypobaric hypoxia (HH), an environmental condition of high altitude encountered by mountaineers, miners, and observatory, rural health, border patrol, and rural education workers, jeopardizes normal physiologic functions in humans. The present study was conducted to evaluate the effects of intermittent HH (IHH; equivalent to 4600 m above mean sea level) on oxidative stress and the protective role of dietary ascorbic acid on rat testis and epididymis. Ten‐week‐old male Wistar rats were assigned to 1 of 6 groups: 1) normobaric (Nx), 2) Nx + physiologic solution (Nx + PS), 3) Nx + ascorbic acid (Nx + AA), 4) IHH, 5) IHH + PS, or 6) IHH + AA. Animals subjected to IHH were exposed for 96 hours followed by normobaric conditions for 96 hours for a total of 32 days. The control groups (2 and 5) were injected with doses of PS, and the treated groups (3 and 6) were injected with doses of AA (10 mg × kg−1 body weight) at an interval of 96 hours. Rats were sacrificed on day 32 after initiation of the protocol. The testis and epididymis were collected to determine the activity and expression of glutathione reductase and the levels of lipid peroxide formation. An epididymal sperm count was also performed in each animal. The results of this study revealed that IHH induced lipid peroxidation, a reduction in glutathione reductase activity in testis and epididymis, and a significant decrease in epididymal sperm count. Treatment with AA prevented these changes. In conclusion, AA was capable of decreasing oxidative stress in testis and epididymis under IHH. This protection by AA of the IHH‐induced lipid peroxidation can be explained in part by the preservation of glutathione reductase activity in these organs.
Estrogen Receptor α and β Polymorphisms Are Associated With Semen Quality
Authors: Lazaros Leandros A. , Xita Nectaria V. , Kaponis Apostolos I. , Zikopoulos Konstantinos A. , Plachouras Nicolaos I. , Georgiou Ioannis A.
Published: July 2010

ABSTRACT: The role of estrogen receptor α (ERα) and estrogen receptor β (ERβ) gene polymorphisms on semen quality is the aim of our study. One hundred fourteen men were examined in the In Vitro Fertilization Unit of Ioannina Medical School, and it was found that 85 men had normal sperm count and 29 were oligozoospermic. The genotype analysis, on DNA extracted from spermatozoa, revealed that in men with oligozoospermia (sperm concentration <20 × 106 spermatozoa/mL), those with ERα 397T/C and 397C/C genotypes had higher sperm motility whereas those with 397T/T genotype had lower sperm motility (P = .003). In addition, men with ERα 351A/A genotype had lower sperm motility compared with 351A/G and 351 G/G genotypes (P = .013). Furthermore, normal‐sperm‐count men with ERα 397T/T genotype had higher sperm concentration compared with 397T/C and 397C/C genotypes (P = .016), whereas men with ERα 351A/A genotype had higher sperm concentration than those with 351A/G and 351G/G genotypes (P = .05). In contrast, no significant associations were found between ERβ (1082G→A and 1730A→G) polymorphisms and sperm concentration or motility. In conclusion, ERα polymorphisms were found to be associated with sperm motility and concentration. supporting the significance of this gene in spermatogenesis and semen quality.
Hepatocyte Growth Factor (HGF) Modulates Leydig Cell Extracellular Matrix Components
Authors: Catizone A. , Ricci G. , Tufano M. A. , Perfetto B. , Canipari R. , Galdieri M.
Published: July 2010

ABSTRACT: Hepatocyte growth factor (HGF) is a pleiotropic factor that plays multiple roles during mammalian development. We previously demonstrated that in the postnatal testes, the HGF receptor, c‐met, is expressed by Leydig cells and HGF increases the steroidogenetic activity of the cells. In the present article, we report that HGF modifies the composition of the extracellular matrix of cultured Leydig cells. We show that HGF increases the metabolic activity of isolated Leydig cells; in particular, the factor increases urokinase plasminogen activator and matrix metalloproteinase 2 secretion. We have also shown that the levels of active transforming growth factor β are increased by HGF. On the contrary, using the Western blotting technique, a strong reduction in the amount of fibronectin present in the culture medium of cells cultured in the presence of HGF has been detected. The presented data demonstrate that HGF modulates several functional activities of Leydig cells, further supporting the hypothesis that this factor has a relevant role in the regulation of mammalian spermatogenesis.
Roles of Androgen Receptor in Male and Female Reproduction: Lessons From Global and Cell‐Specific Androgen Receptor Knockout (ARKO) Mice
Authors: Zhou Xinchang
Published: July 2010

ABSTRACT:The androgen receptor (AR), a member of the nuclear receptor superfamily, is a ligand‐dependent transcription factor involved in regulating expression of an array of androgen‐responsive genes. AR‐mediated androgen actions play the important roles in male and female reproductive development and function. AR mutations can cause a diverse range of diseases, such as testicular feminization mutation (Tfm) syndrome, prostate cancer, and Kennedy's disease. However, because of a lack of genetic models, the molecular mechanisms involved in the physiological and pathological effects of androgen–AR function in male and female reproductive health remains largely unknown. To get a better insight into the molecular working mechanisms of the AR, a global and several cell‐specific conditional knockout mouse models have been developed. These models are reviewed here, and the phenotypes of the different cell‐specific androgen receptor knockout (ARKO) mice are compared with those of the global ARKO mice.
A search of Brassica SI-involved orthologs in buckwheat leads to novel buckwheat sequence identification: MLPK possibly involved in SI response
Authors: Banovic Bojana , Miljus-Djukic Jovanka , Konstantinovic M. , Maksimovic Vesna
Published: July 2010

Self-incompatibility (SI) systems, gamethophytic (GSI) and sporophytic (SSI), prevent self-pollination in angiosperms. Buckwheat displays heteromorphic SSI, with pollination allowed only between different flower morphs - thrum and pin. The physiology of thrum and pin morph SI responses are entirely different, resembling homomorphic Brassica SSI and Prunus GSI responses, respectively. Considering angiosperm species may share ancestral SI genes, we examined the presence of Brassica and Prunus SI-involved gene orthologs in the buckwheat genome. We did not find evidence of SRK, SLG and SP11 Brassica or S-RNase and SFB Prunus orthologs in the buckwheat genome, but we found a Brassica MLPK ortholog. We report the partial nucleotide sequence of the buckwheat MLPK and discuss the possible implications of this finding.
Genetic diversity of Austrian pine (Pinus nigra Arnold) populations in Serbia revealed by RAPD
Authors: Lucic A. , Mladenovic-Drinic Snezana , Stavretovic N. , Isajev V. , Lavadinovic Vera , Rakonjac Ljubinko , Novakovic Marijana
Published: July 2010

The ability of random amplified polymorphic DNA (RAPD) to distinguish among populations of Austrian pine from Serbia was evaluated. Ten arbitrary 10mer primers employed in the analysis produced 113 fragments of which 100 were polymorphic (88.5%). All populations had specific RAPD phenotypes. Certain rare and genotype specific bands were identified which could be effectively used to distinguish the populations. Polymorphism in RAPD markers among P. nigra population was high and sufficient to distinguish each of the populations. The results obtained suggest that RAPD markers are valuable for the genetic diversity estimation in Pinus nigra and for the study of the divergence among populations.
The effects of chronic exposure to electromagnetic fields on thyroid parafollicular cells in rats
Authors: Rajkovic Vesna , Matavulj Milica , Vuckovic D.
Published: July 2010

Withdrawn; published twice because of tehnical error. Link to the Editorial Decision 10.2298/ABS1004251U
Antibacterial and antifungal activity of the liverwort (Ptilidium pulcherrimum) methanol extract
Authors: Veljic M. , Ciric Ana , Sokovic Marina , Janackovic P. , Marin P.D.
Published: July 2010

The antimicrobial activity of the methanol extract from the liverwort, Ptilidium pulcherrimum was evaluated against five bacterial and six fungal species. In vitro antibacterial activity was assessed by disc diffusion and microdilution methods. The extract showed a stronger effect against tested Gram (+) than Gram (-) bacteria. The antifungal activity of the methanol extract was tested using a microdilution method. The methanol extract showed strong antifungal activity. The best antifungal activity was achieved against Trichoderma viride compared to the synthetic fungicide bifonazol.