bluuebunny/crossref_metadata_2025 huggingface dataset:
Stimulating Khuff Gas Wells with Smart Fluid Placement
Authors: Garzon Francisco , Amorocho Jose Ricardo , Al-Harbi Moataz , Al-Shammari Nayef S. , Al-Ruwaished Azmi , Ayub Mohammed , Kharrat Wassim , Burgrov Vsevolod , Jacobsen Jan , Brown George , Noya Vidal
Published: January 2010

The objective of many matrix acidizing treatments in the Khuff carbonate formations is to remove drilling damage and enhance productivity after the drilling process. Open hole and multilateral completed wells, present several challenges that prevent an optimum intervention with coiled tubing (CT). Traditional practices have been limited to spot stages of pre-flushes, acid, and diversion systems in front of the formation from toe to heel without proper control over the placement process.

Using an innovative workflow, interpretation of distributed temperature surveys (DTS) responses, correlated with reservoir data, assists in selectively placing fluids, maximizing the contact of stimulation fluids with the targeted formation sections. Two field applications, in dual-lateral horizontal open hole gas producers, that demonstrate how to optimize a stimulation treatment as it occurs, were implemented in a field in the Kingdom of Saudi Arabia.

In both cases, selective access to pay zones in each lateral was confirmed with DTS profiles. Following the pre-flush and the first acid pass, DTS measurements indicated acid effect over the permeable zones but also detected fluid movement towards non gas bearing thief zones. Foam and energized visco-elastic diverting acid fluids were used to divert acid to the target zones avoiding the lost of all stimulation fluids to the toe in one case and to the heel in the other well. After treatment, the gas production increased from zero to more than two times the expected rate in both wells.

Understanding of the flow patterns as fluids are placed in the wellbore was possible. Changes to the fluid placement schedule during the job resulted in optimum acid coverage and efficient diversion confirmed by the downhole measurements. The identification of the thief zones was critical to avoid wasting fluids. This experience, the first ever gas wells in Middle East, represents an opportunity for un-locking production potential in similar gas developments.
Simulating Model to Reduce Detrimental Acidizing in Tabnak Gas Field
Authors: Farrokhrouz M , Asef M R
Published: January 2010

Dalan and Kangan formations are the most important host gas reservoirs in Iran. These geological formations are extended to other regions, and they are famous as Khuff formation in the Middle East. They are mainly composed of limestone and dolomite with some inter-beds of shale. So far many reservoirs in Iran are hosted by Asmari carbonate formation. However, acidizing in other hydrocarbon formations (Asmari formation) is accomplished similarly. Conventional acidizing operations were performed on Dalan and Kangan formations in one of the gas fields in south of Iran. Substantial reduction of produced gas was observed over a short period of time. For this reason a comprehensive engineering geological site investigation was accomplished to explain the symptoms and avoid possible further deterioration. Connate water samples from the well while production, showed some unexpected results. Different chokes were tested to see if the amount of impurities in the sample would change. To reduce the amount of water accompanied with produced gas, a different choke was selected; but the result was not satisfactory enough based on refinery report.

Therefore, the geological features of the well were gathered based on well sketch and logging data. The phase equilibrium of the reservoir rock before and after acidizing was simulated using a software. The results of chemical lab were analyzed to check the kind of the salts in the well. Laboratory chemical experiments were accomplished to explore produced salts in the well. Further investigation revealed that the choke size was not suitable, and inappropriate acidizing could deteriorate the situation. Based on this research, a number of recommendations were suggested to improve the circumstances of production rate. The authors suggested more carefully designed techniques of acidizing to be applied. The results of this research may be used to prevent geomechanical destabilization around the wellbore in similar cases.
Field Trials of a Novel Fiber-Laden Self-Diverting Acid System for Carbonates in Saudi Arabia
Authors: Leal Jauregui Jairo A.. , Malik Ataur R.. , Walter Nunez Garcia , Solares Ricardo J.. , Tomislav Bukovac , Gurmen Nihat M..
Published: January 2010

Acid stimulation of carbonate formations using hydrochloric (HCl) acid-based systems to improve hydrocarbon production or water injection has been a common practice since the early days of the oil and gas industry. The challenge of achieving full zonal coverage with the stimulation fluid still persists. This task is even more difficult in highly slanted layered, naturally fractured reservoirs exhibiting high permeability and porosity contrast.

During acid stimulation treatments, the fluid has a natural tendency to take the path of least resistance, penetrating layers with the highest porosity and permeability while little or no acid is injected into lower-quality zones. Excessive fluid loss to these high-quality thief zones results in a nonhomogenous distribution of stimulation fluids across the targeted interval. These higher-quality zones are essentially over stimulated, allowing them to contribute the most to post-treatment production. This leaves neighboring lower-quality zones unstimulated, preventing them from reaching their maximum potential.

A novel fiber-laden polymer-free self-diverting acid system was introduced in Saudi Aramco to improve zonal coverage across the entire interval of interest in vertical and highly slanted wells during stimulation treatments. This diversion system combines fiber and a self-diverting acid, which utilizes a nondamaging viscoelastic surfactant that gels as the acid spends. The combination of the self-diverting acid and fiber enhances the diversion process by combining the aspects of both particulate and viscosity-based diversion techniques. The fluid system has a distinct advantage in that it does not contribute to reservoir damage as the viscoelastic surfactant will break down upon contact with hydrocarbons, and the fiber will dissolve with time and temperature.

The fiber-laden self-diverting acid system has been applied in new developments and producing gas wells in the Khuff reservoir of Saudi Aramco with impressive results. The diversion and acid reaction signatures were evident in the acquired treating pressure plots during acidizing with the fiber-laden polymer-free self-diverting acid system. The initial results indicated substantial pressure responses and excellent gas production performance.
Effective Ways to Avoid Barite Sag and Technologies to Predict Sag in HPHT and Deviated Wells
Authors: Amighi Mohammad Reza , Shahbazi Khalil
Published: January 2010

Barite Sag is an oilfield term used to describe significant density variations while circulating bottoms up after a trip, logging run or other operations that require the mud to remain static for an extended period of time. Sag is caused by static and/or dynamic settling followed by slumping of the weighted material. Static sag, as the name suggests is caused when circulating is stopped for an extended period of time, and the weighting agents begin to settle under the influence of gravity. Due to slumping, dynamic sag occurs frequently in inclined holes. However, the problem has been exacerbated by the increased frequently of high-angle wells with the associated increase in particle settling rate which occurs in an inclined fluid column. The settling of solids is enhanced by convective currents created by density differences in the fluid across the annulus cross section. This effect is frequently referred to as Boycott effect.

This paper presents the most effective ways to avoid the occurrence of barite sag in high-pressure high temperature (HPHT) drilling operations, and in high-angle wells. The ways such as replacing barite by other weighted materials such as Ilmenite or Manganese tetraoxide. Furthermore, it is suggested to use a cesium formate based drilling fluid or polymer-coated ultra-fine barite for drilling HPHT wells. Moreover, different technologies to predict dynamic sag such as, flow loop tests and modified rotational viscometer tests, are introduced.
Integration of Conventional Logs, Core, Borehole Images, and 3D Seismic, A Rule of Geological Modeling in Tight Clastics Gas Deep Reservoirs, Oman
Authors: Farag Ashraf , Al Hasani Hanaa , Al Lawatia Redha H.
Published: January 2010

Integration of conventional logs, core and 3-D seismic with borehole images provide a reliable and decent approach to geological modeling in tight clastics deep gas reservoirs in Oman. The Studied field is of Cambrian-Ordovician age. The field structure is North-South elongated domal anticline associated with a salt pillow.

The main hydrocarbon bearing and producing reservoirs are predominantly of continental to marine environments in the deepest part: aeolian dominated formation (A) to sabkha dominated formation (B) in middle intervals and non-marine (coastal plain) to shallow marine (intertidal-subtidal) (C) sandstone members at the shallowest levels.

The seismic image quality at the reservoir levels are poor, mainly due to the weak acoustic impedance contrast between deep reservoirs and the overlaying shale, besides the presence of multiple noises further obscured the event, in addition to limited number of core intervals all over the field.

In order to refine the structural, depositional model and facies distribution for clastic tight gas deep reservoirs, a detailed integrated borehole resistivity images log interpretation with the available data was performed. Structural dip, structural features like faults locations and their strike and dip angles, sub seismic faults for field transmissibility, and compartments, natural fractures, sedimentological and facies analysis where core - logs comparison was done to improve the rock typing which later correlated to the petrophysical properties, are the major achievements from this study. The study has also analyzed the major accumulations and the paleo-current and paleo wind directions over the reservoirs units by predicting their paleo-drainage and sediments entry points. These results formed valuable input to the field geological modeling.

The exercise of tying the above results with seismic data was carried out with a very effective methodology for the generation and significant improvement of a new geological model to support further development and added new reserves in tight gas reservoirs.
Estimation of Production Potential and Reserves of Jauf Gas Reservoir of Bahrain Field
Authors: Al Owainati Ebrahim , Al Muftah Ali , Kumar K.. , Murty C.R.K.. R.K.
Published: January 2010

In recent years Bahrain has experienced a rapid growth in gas demand for industrial use, electricity generation, gas injection, and artificial lift. The main source of gas for these needs is the Khuff reservoir only. This recognition of this fact has been the main driver for the exploration of the deep gas prospects in Bahrain field.

Jauf formation has been found to have hydrocarbon potential regionally. It has been found hydrocarbon bearing in the flanks of Ghawar anticline. Jauf sandstone has also been found to be highly prospective exploration target in the Bahrain field, since it has been proved gas bearing in the crestal well. The well flowed with moderate gas rates before sanding up.

In addition to the crestal well, five other wells penetrated Jauf zone. Three wells gave clear gas shows and two peripheral wells tested water. Long testing was done in one of the three wells to produce gas from Jauf. This well produced from Jauf for more than two years before Jauf was plugged and more prolific layers were opened in the well. Jauf produced at an average rate of 15 MMSCFD.

In order to estimate the gas reserves and the production potential in Jauf, uncertainties with gas reserves estimate and the reservoir continuity should be considered. Rock properties, drive mechanism, fluid properties, pressure, gas quality, and the production tests play vital role in estimating the reserves. Therefore, two approaches were used to estimate the Jauf gas reserves: around gas tested well-bores and as a continuous medium. The paper will describe each approach and further will present the results.

As there are good reasons for the Jauf reservoir to be continuous within the Bahrain field area, a simulation model was built considering the data from all the drilled wells using only the lower limits for all the reservoir parameters like porosity, net thickness, and saturation. Performance forecast was also carried out to evaluate the sustainability of the plateau gas rates, which will be discussed in this paper.
Cement Considerations for Tight-gas Completions
Authors: Darbe Robert , Ravi Kris
Published: January 2010

Recent advancements in completion technology have made tight-gas bearing formations more attractive for production. However, long horizontal sections with multiple fracture treatments can influence the effectiveness of the seal provided by the cemented annulus which, in turn, can affect the productivity of the completed well. Therefore, planning for cementing, followed with proper design and execution, is important to overcome the challenges associated with tight-gas well completions and production.

It is challenging to centralize casing strings placed in highly deviated wellbore sections. Poor centralization results in a non-uniform annular-flow profile as fluids tend to flow along the path of least resistance. If this phenomenon exists during cement-slurry placement, an uncemented channel can result on the narrow side of the annulus creating a flow path for fluids to migrate within the annulus.

Effective cement slurry placement resulting in an initial annular seal does not guarantee that the seal will be maintained through subsequent completion events. A cement sheath is, by nature, brittle when it is exposed to the stress environment that high pressure hydraulic stimulation produces. The cement sheath can crack, resulting in unwanted flow paths. In addition, fracture attempts early in the completion of a tight-gas well can weaken the hardened cement through fatigue, breaking the cements' sealing capability.

The lack of a cemented annular seal can result in the inability to control wellbore fluids affecting both the fracture treatments and subsequent production. If the cement sheath allows fracturing fluids an alternative path, then fracture initiation points might not occur at the desired location, minimizing the stimulation effectiveness. Production gases can also follow an alternative path, which allows for uncontrolled flow to thief zones and to the surface.

This paper discusses cement-slurry placement and enhanced sealing properties that a cement system should possess to help withstand the tight-gas completions.
Overcoming the Cementing Challenges in Deep Gas Environment
Authors: Ravi Kris , Darbe Robert
Published: January 2010

Developing and producing a deep gas asset is a challenge because the reservoir is often of low permeability, commonly referred to as tight gas. In some cases, the wells are drilled under-balanced to prevent damaging the reservoir. Very often, it is necessary to drill through weak, depleted zones to reach the reservoir. These factors pose unique challenges to cementing materials used and methods applied. These challenges need to be understood in detail and solutions designed and implemented successfully for economical production of gas from deep environment.

Properties of cementing fluids, spacer and cement-slurry, should be optimized to enable successful cementing when the well is drilled under-balanced. The importance of properties such as fluid loss, density, and resistance to formation fluid influx are discussed and presented. Spacer fluids and cement-slurry need to be optimized based on reservoir parameters to help prevent fluid influx from the formation. The rate at which the slurry develops static gel strength is an important parameter to help prevent formation fluid such as gas from entering the annulus and either flow to other zones or come to the surface.

When drilling through depleted, weak zones the circulating and hydrostatic pressure should be minimized to help prevent losses to the formation. The density and rheology of the cementing fluids influence these values and should be optimized to help ensure successful placement of cement-slurry when there is a risk of losses. Design of the spacer fluid and cement-slurry to help prevent losses are discussed and presented. There are distinct advantages of using different chemical treatments ahead of the cement-slurry to control the losses. Different chemical treatment options will be presented and discussed.

The solutions discussed in this paper should help in constructing and operating the deep gas wells economically and safely.
Development and Optimization of 12-in. PDC Bit for Powered Rotary Steerable Systems in Deep Gas Drilling in Saudi Arabia
Authors: Reda Saeed Al , Kubaisi Abdullah , Nawaz Khalid , Jamil Muhammed Fouad , Alvarez Octavio , Qattawi Baseem , Verma Jaywant , Ganda Sukesh
Published: January 2010

Directional drilling the 12-in. curve section in the deep gas fields in Saudi Arabia is very challenging because of the hard formations and harsh drilling conditions. The section consists primarily of hard limestone and dolomites interbedded with anhydrite. The main challenges of drilling this section include multiple bit trips and reduced rates of penetration (ROP).

To overcome these challenges, the operator, directional drilling service company, and drill bit company in collaboration developed an optimization process to create and evolve a polycrystalline diamond compact (PDC) bit design to be used on powered rotary steerable systems (PRSS).

The objective of the optimization process was to increase the ROP and the durability of existing PDC bits to eventually lead to drilling longer intervals by minimizing the number of bit trips while drilling with PRSS. The challenge required the development of a new PDC technology in conjunction with optimized drilling practices and a reliable drive system.

The challenges were overcome by implementing the specific bit design algorithms incorporated with new cutter technology, and using drilling simulation software to optimize the bit cutting structure design in directional drilling environment. Significant improvements in bit design were achieved after closing the model/measure/optimize loop. Through field testing, drilling parameter evaluation, and drilling simulation, a new 12-in. PDC bit was designed that established benchmark performances in the deep gas operations in the Ghawar field.

The successful development of the PDC bit in conjunction with the PRSS system led to record runs in the 12-in. build section. Casing-to-casing sections were drilled with an improved ROP of approximately 125%, compared to that of a conventional motor. This paper reviews the bit design and optimization process to develop the fit-for-purpose PDC bit that helped to improve the drilling performance, significantly reduce rig days, and enable early delivery of the wells in challenging deep gas drilling in Saudi Arabia.
Breakthrough PDC Technology Used in Saudi Arabia Deep Gas Wells to Significantly Reduce Drilling Time
Authors: Alvarez Octavio , Jamil Fouad , Qattawi Bassem , Olorode Akin O.
Published: January 2010

Drilling the intermediate sections in the deep gas fields of Saudi Arabia is challenging because of a long, intricate geological sequence consisting of hard carbonates (limestone and dolomite) interbedded with anhydrite. Historically, the primary operator has attempted to drill the section using both roller cone tungsten carbide (TCI) and polycrystalline compact (PDC) technology. PDC bits provided better penetration rate and durability, as compared to TCI bits. However, several PDC bits were required to drill the section, which increased the time needed for drilling and tripping at relatively deep intervals. The increased time exposes the well to risks when the hole is open for long intervals.

After further analyses and a systematic bit optimization process, three new PDC bit designs were created and used, which established new benchmarks in two of the deep gas fields. Meeting the objective of minimizing the number of bit trips by enhancing PDC bit performance and bit durability to drill longer intervals with a higher penetration rates required a new PDC bit technology in conjunction with optimized motor drive. To address the challenge, the operator, bit vendor, and other service companies worked together to develop an optimized solution to drill these sections.

The paper reviews the findings of the study in drilling the intermediate sections in two of the challenging deep gas fields. The study shows that PDC bit damage from encountering harder stringers was the primary impediment to achieving better performance. The impediment was overcome by implementing the new cutter technology and drilling simulation software to optimize the cutting structure design. The paper demonstrates the improvement in the deep gas fields in Saudi Arabia by comparing the performance of the most recent wells, in which the new technologies were implemented, to the earlier wells to illustrate the significant time and drilling cost reduction.
Combined Capillary Pressure and Resistivity Index Measurements in Tight Gas Sands Using Vapor Desorption Method
Authors: Dernaika M.R.. R.
Published: January 2010

This paper presents work on laboratory advances that have been developed to measure capillary pressure and electrical property measurements under low water saturation conditions. The paper discusses in some detail the various capillary pressure techniques utilized in the oil and gas industry and gives some insights on the Kelvin equation's applicability in tight gas sands. Detailed comparisons are shown between vapor desorption capillary pressure and mercury injection data a saturation offset that could be attributed to the non-wetting nature of the fluids and possible rock matrix alteration. The proposed calibration of the mercury data on tight sands is then considered for tight gas carbonate reservoirs.
Successful HPHT Application of Potassium Formate/Manganese Tetra-Oxide Fluid Helps Improve Drilling Characteristics and Imaging Log Quality
Authors: Al-Saeedi M. J. , Al-Khayyat B.. , Al-Enezi D.. , Aslan A.. , Luzardo J.. , Carrera C..
Published: January 2010

Unconventional reservoirs associated with the presence of fractures have been identified in the Jurassic horizons in the Raudhatain field in North Kuwait. These reservoirs contain high-quality light oil and gas under HPHT conditions with associated H2S and CO2. The operator in this field is presently developing these gas/light oil reserves under the ‘North Kuwait Gas Development Project, The well discussed in this paper is one of a number of new production wells.

Historically, Jurassic wells in this field have been drilled using conventional barite-weighted, oil-based mud (OBM) with densities up to 18.5 ppg. However, the challenge to maximize the amount and quality of reservoir data collected and to reduce any impact on the formation caused by OBMs led to a search for an optimized water-based mud (WBM) system as an alternative.

A WBM formulated with saturated potassium-formate brine, weighted with manganese tetra-oxide, was selected for the following characteristics: higher base-fluid density, non-damaging nature, robust behavior in HPHT environments, and the possibility of better quality image logs.

The well reached 16,530 ft., in a 6–in. hole, with bottomhole temperatures around 280°F. The fluid was thermally resistant, exhibiting very low HPHT filtrate loss and highly stable rheological properties. The maximum fluid density was 16.2 ppg, with no evidence of settling of weight material, even after three days of static conditions.

A complete suite of logs was run successfully. The elemental capture spectroscopy (ECS), along with sonic and neutron porosity logs provided good data quality, and the image logs showed excellent resolution.

This paper will present all aspects of the planning, design, and utilization of this new drilling fluid. It will focus on lessons learned and conclude with recommendations for further optimization of the design of these drilling fluids.
Long-Lasting Experience In Environmental Protection During Sour Gas Reservoir Exploitation
Authors: Hrncevic L.. , Simon K.. , Kristafor Z.. , Malnar M..
Published: January 2010

Since fossil fuels are still dominant sources of energy supply, in order to meet rising energy demand, petroleum industry is called upon not just to provide an effective management of oil and gas reserves, but also to manage to do that in safe and efficient manner with as low as practically possible ecological footprint. Consequently, also taking into account the fact that conventional oil and gas reserves are declining, petroleum companies are forced to develop and adopt new technologies to increase oil and gas recovery and to expand their upstream activities to still unexploited areas which often implies development of deep- buried oil and natural gas reservoirs characterized with unfavourable reservoir conditions such as high temperature and pressure and even certain amount of impurities.

Croatian experience with the natural gas production from deep- buried reservoirs is based on the development of several gas fields in the north- western part of Croatia. The development of the largest natural gas fields in Croatia, Molve, Stari Gradac and Kalinovac gas fields has begun at the beginning of the 1980's. The main characteristic of all the mentioned fields are extremely unfavourable reservoir conditions with reservoir depth over 3000 m, high initial reservoir pressures (over 450 bar), high temperature (180°C) and significant share of CO2, (10 - 54%) H2S (800 ppm) as well as some other non- hydrocarbon compounds like mercaptans (30 mg/m3) and mercury (1000 - 1500 µg/m3). In the last 25 years in the same region several other gas fields with the similar reservoir conditions were discovered and developed. Today, petroleum industry in Croatia has almost 30 years of experience in processing sour natural gas with well established methodology of auditing processing plant outlet gas influences on the environment. These experiences and future plans regarding this subject will be presented in this paper.
Finite Element Simulation of Downhole Stresses in Deep Gas Wells Cements
Authors: Nabipour A.. , Joodi B.. , Sarmadivaleh M..
Published: January 2010

Deep gas reservoirs are going to play more important roles in meeting growing demand of natural gas throughout the world. Due to extreme conditions of downhole stresses, pressure and temperature that occur in deep gas wells, maintaining cement mechanical integrity and zonal isolation have become critical concerns of industry during drilling, completion, and production of such wells. Cement sheath is expected to provide a flawless annular seal between casing and formation along the wellbore. However; cement failure cases which are being reported regularly show that there is still need for understanding extreme downhole conditions and the behavior of cement sheath experiencing such an environment. Although Uniaxial Compressive Strength (UCS) of cement is commonly regarded as the most important mechanical property of cement, recent theoretical and experimental results show that other mechanical properties of cement can be even more determinative in its failure.

In this study, Finite Element Method (FEM), a widely-used robust numerical tool, is used for simulation of the downhole environment by modeling temperature, pressures, stresses, downhole materials and their interactions. Using this approach magnitude, direction and type of induced stresses in casing, cement, and formation have been determined. Furthermore; a series of sensitivity analyses was performed to reveal the effects of variation of various parameters such as casing internal pressure, differential horizontal stress and casing eccentricity, on the induced stresses in the cement sheath.

Radial, tangential and von Mises stress profiles in the deep gas wells cements were investigated. Furthermore, the effect of casing internal pressure, differential horizontal stress and casing eccentricity were studied in the model. Results show that deep gas wells’ cements experience extreme amounts of thermal and mechanical stresses and special consideration is required in cement selection.
New Generation of MWD, LWD, and Image Logging Opens New Possibilities for Data Acquisition and Evaluation in Deep Gas Reservoirs
Authors: Malcore Eric C. , Qutob Hani , Kuchinski Robert
Published: January 2010

Drilling deep gas wells poses a set of significant technical challenges, many of which approach or push the boundaries of equipment operational limits. The need for formation evaluation data in the deep gas reservoirs can be explained by the fact that relatively little is known about these reservoirs as data acquisition has been previously limited by temperature, pressure and hole size limitations of the instrumentation in older WL and LWD tools. Well bores of 5 in. or less may prohibit conventional logging-while-drilling (LWD) tools from acquiring necessary data. In addition, the consequences that high pressure has on mud systems which cause LWD and MWD data pulses to be compromised. Because standard LWD equipment had experienced numerous failures at such difficult down hole conditions, a new class of LWD and imaging tools was developed to address this challenging situation, This new class of tools opens new possibilities for data acquisition and evaluation in deep gas reservoirs. The paper will discuss:

What technology exists today? The challenges in developing these technologies? The advantages and limitations of the technology.

The measurements that will bring benefit in understanding the reservoirs such as real time imaging for fracture ID, (fracturing is a critical component as these reservoirs are rather tight and require natural or induced fracturing to enhance the permeability) The features and capabilities of the new tools will be discussed in this paper together with a brief introduction of few case studies representing the hot drilling in the North Sea, the heavy mud in China and the successful acquisition of high-quality data in a deep and slim hole well in Italy.
Hydraulic Fracturing Under Extreme HPHT Conditions: Successful Application of a New Synthetic Fluid in South Texas Gas Wells
Authors: Funkhouser Gary P. , Holtsclaw Jeremy , Blevins Joy J.
Published: January 2010

A new hydraulic fracturing fluid has been developed that is capable of stimulating high pressure/high temperature (HPHT) wells at 450°F without the need for cooling preflushes. Good viscosity at fluid temperatures as high as 450°F gives the synthetic fluid the potential to provide substantially better proppant placement than polysaccharide-derivative gels. The gelling agent is based on a terpolymer of 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, and acrylic acid that can be crosslinked with zirconium. The crosslink onset temperature can be varied over the range of 100 to 280°F, allowing optimization for particular well conditions. A delayed acting oxidizing breaker can be added to accelerate the gel's degradation, allowing rapid flowback and early production. The gelling agent is provided to the wellsite as a liquid-gel concentrate that is designed to be mixed and pumped with conventional fracturing equipment and procedures.

This paper discusses the laboratory testing, treatment design, and job execution leading to the successful hydraulic fracturing of two South Texas gas wells at depths of 23,300 and 18,900 ft with bottomhole static temperatures of 450°F and 433°F, respectively. The jobs were pumped as designed, with 190,000 lbs. of high-strength, resin-coated proppant placed in each zone at concentrations up to 9 lb/gal. Average treating pressures were 13,100 and 11,250 psi with slurry rates of 21 and 25.7 bbl/min, respectively. Cleanup was rapid, with gas flowing to the sales line the day after the treatment at a rate in excess of 4,000 MCF/D; in the case of the second well.
New 9-7/8-in. HPHT Permanent Packer with New Back-Up System Provides North Sea Operator with Effective Solution for Damaged or Worn Casing
Authors: Robb Thomas , Valentine Ernie
Published: January 2010

A major operator in the North Sea had experienced a problem with worn casing at the packer setting depth of an existing HPHT well, causing a leak into the production annulus. A workover was required, and a calliper survey conducted after retrieving the tubing revealed two sizeable grooves along the longitudinal axis of the casing at 120° to each other.

This paper discusses the successful qualification and installation of an HPHT permanent packer for worn casing. Permanent packers are qualified by ISO 14310 V0 in a test fixture to meet the ISO 11960 internal casing dimensions; however, they do not account for any wear or damage in the casing. A test program was developed to test the packer at HPHT well conditions and in worn casing. The test program consisted of the following:

Install the packer in 9-7/8-in casing and flow test to 3 bpm at 180°F to verify that the circulation around the packer did not damage the Aflas® element. Perform an application test using synthetic oil to mimic packer loading until failure, including setting, production, and hot/cold shut in.; apply 9,000 psi annulus pressure to support the casing during testing. In this case, the maximum temperature was 343°F or above for over 200 hours. Perform a modified ISO 14310 V0 test at 450°F with 15,000 psi differential pressure and 400,000 lbf tension and compression.

The packer passed all tests with no extrusion of the three-piece multi-durometer Aflas® element, and no leaks were detected at any of the load points in the application (liquid) test or modified ISO V0 gas test.

The discussion will include information on the packer design, HPHT test in worn casing, and casing acceptance criteria. This test was the first packer test performed in worn casing that demonstrated the capability of the compliant back-up systems to support the entire element in worn casing and at HPHT conditions.
Improved Permeability Modeling in a Saudi Arabian Deep Gas Reservoir Including Measurement Uncertainties
Authors: Forsyth David
Published: January 2010

A translation scheme must be established to link core properties, such as rock type and permeability, from core intervals to non-cored intervals. Such a translation determines accurate and consistent permeability predictions across the field. This study focuses on an Early - Middle Devonian sand-dominated, tidal-estuarine depositional sequence. The formation is characterized by permeability variations caused by rapid facies changes, modified by a highly variable diagenetic overprint. Reservoir production is characterized by relatively thin limited intervals with prolific flow; and other intervals where the flow is low, despite permeability data, which suggest better productivity. These properties reflect a high uncertainty scatter in the permeability distribution. Existing permeability modeling techniques often fail to capture the actual range and scatter of permeability present in the formation: At the low porosity range the modeled permeability overestimates the potential flow and underestimates the performance of the prolific intervals.

This paper presents an approach to improve the permeability prediction by reducing the permeability uncertainty scatter using electrofacies groupings; then, by including the remaining permeability uncertainty scatter in the modeled result. Furthermore, recently acquired and more accurate core permeability measurements at the micro-Darcy range have improved the definition of the low permeability range for this reservoir through the higher resolution measurement.

The results of this work were an improvement in the permeability predictive model. In particular, the calibration of the low permeability intervals was better defined through an improved stress correction. At the high permeability end the identification of productive intervals was improved by the reservoir quality clustering approach combined with the core permeability statistics.

This approach results in improved reservoir characterization with better predictive capacity through better modeling of the dynamic permeability range.
The God that Failed: Free Market Fundamentalism and the Lehman Bankruptcy
Authors: Ferguson Thomas , Johnson Robert
Published: January 2010

Thomas Ferguson of U. Mass, Boston and Robert Johnson of the Roosevelt Institute argue that letting Lehman fail--not the later bailout announcement--triggered the financial collapse, contrary to the views of John Taylor and John Cochrane and Luigi Zingales.
Editorial: Special Issue Contributed from CHEMECA 2008-Mathematical Modeling
Authors: Nelson Mark I , Young Brent , Sidhu Harvinder S
Published: January 2010

The papers in this issue of Chemical Product and Process Modeling are substantially those that arose from special sessions on mathematical modeling" at the 36th Australasian Chemical Engineering Conference (held between 28th September to 1st October 2008, in Newcastle, Australia). The papers in this special issue are available at: www.bepress.com/cppm/vol4/iss3.
Tax Law Asymmetries and Income Shifting: Evidence from Japanese Capital Keiretsu
Authors: Onji Kazuki , Vera David
Published: January 2010

While the asymmetric treatment of positive and negative income creates clear tax incentives to shift income among a group of closely related corporations, attempts to document the impact of such behavior on economic outcomes are relatively sparse. We aim to provide evidence on tax-motivated transfers from a large dataset of Japanese corporate groups. Using company level data on 33,340 subsidiary time pairs from 1988, 1990, and 1992, we consider testable implications of income shifting in a theoretical model tailored to the Japanese institution of the early 1990s and empirically examine the spread of the profitability distribution, the attrition rate of loss-making subsidiaries, and the propensity to report zero profit. The findings suggest that income shifting was pervasive when Japan had not adopted a formal allowance for group-level tax. The result underscores the importance of accounting for the inter-relatedness of companies, in designing a corporate income tax.
The Duration of Paid Parental Leave and Children's Scholastic Performance
Authors: Liu Qian , Skans Oskar Nordstrom
Published: January 2010

We study how the duration of paid parental leave affects the accumulation of cognitive skills among children. Using a reform which extended parental leave benefits from 12 to 15 months for Swedish children born after August 1988 we evaluate the effects of prolonged parental leave on children's test scores and grades at age 16. We show that, on average, the reform had no effect on children's scholastic performance. However, we do find positive effects for children of well-educated mothers, a result that is robust to a number of different specifications. We find no corresponding heterogeneity relative to parental earnings or fathers' education, or relative to other predictors of child performance. We find no effects on intermediate outcomes such as mothers' subsequent earnings, child health, parental fertility, divorce rates, or the mothers' mental health. Overall the results suggest positive causal interaction effects between mothers' education and the amount of time mothers spend with their children. Since the institutional context is one in which the alternative is subsidized day care, the results imply that subsidizing longer parental leave spells rather than day care reinforce the relationship between maternal education and school outcomes.
Exercise-Induced Hormesis may Help Healthy Aging
Authors: Ji Li Li , Dickman Jonathan R. , Kang Chounghun , Koenig Ryan
Published: January 2010

Hormesis plays a critical role in producing some major benefits derived from physical exercise. However whether these known cellular mechanisms are applicable to ameliorate age-related deterioration of muscle function is not entirely clear. The present communication proposes that antioxidant adaptation, the peroxisome proliferator-activated receptor gamma coactivator (PGC)-1α activated mitochondrial biogenesis, and eccentric contraction-induced, cytokine-propelled muscle inflammation could be important redox-sensitive pathways by which exercise-induced disturbance in oxidant-antioxidant hemeostasis may serve as a heretic stimulus to promote adaptations that help healthy aging and improve the quality of life.
Genetic Deletion or Pharmacological Inhibition of Dipeptidyl Peptidase-4 Improves Cardiovascular Outcomes After Myocardial Infarction in Mice
Authors: Sauvé Meghan , Ban Kiwon , Momen M. Abdul , Zhou Yu-Qing , Henkelman R. Mark , Husain Mansoor , Drucker Daniel J.
Published: January 2010

OBJECTIVE

Glucagon-like peptide-1 (7-36)amide (GLP-1) is cleaved by dipeptidyl peptidase-4 (DPP-4) to GLP-1 (9-36)amide. We examined whether chemical inhibition or genetic elimination of DPP-4 activity affects cardiovascular function in normoglycemic and diabetic mice after experimental myocardial infarction.

RESEARCH DESIGN AND METHODS

Cardiac structure and function was assessed by hemodynamic monitoring and echocardiography in DPP-4 knockout (Dpp4−/−) mice versus wild-type (Dpp4+/+) littermate controls and after left anterior descending (LAD) coronary artery ligation–induced myocardial infarction (MI). Effects of sustained DPP-4 inhibition with sitagliptin versus treatment with metformin were ascertained after experimental MI in a high-fat diet–streptozotocin model of murine diabetes. Functional recovery from ischemia-reperfusion (I/R) injury was measured in isolated hearts from Dpp4−/− versus Dpp4+/+ littermates and from normoglycemic wild-type (WT) mice treated with sitagliptin or metformin. Cardioprotective signaling in the murine heart was examined by RT-PCR and Western blot analyses.

RESULTS

Dpp4 −/− mice exhibited normal indexes of cardiac structure and function. Survival post-MI was modestly improved in normoglycemic Dpp4−/− mice. Increased cardiac expression of phosphorylated AKT (pAKT), pGSK3β, and atrial natriuretic peptide (ANP) was detected in the nonischemic Dpp4−/− heart, and HO-1, ANP, and pGSK3β proteins were induced in nonischemic hearts from diabetic mice treated with sitagliptin or metformin. Sitagliptin and metformin treatment of wild-type diabetic mice reduced mortality after myocardial infarction. Sitagliptin improved functional recovery after I/R injury ex vivo in WT mice with similar protection from I/R injury also manifest in hearts from Dpp4−/− versus Dpp4+/+ mice.

CONCLUSIONS

Genetic disruption or chemical inhibition of DPP-4 does not impair cardiovascular function in the normoglycemic or diabetic mouse heart.
Potential Mediators of Diabetes-Related Hearing Impairment in the U.S. Population
Authors: Bainbridge Kathleen E. , Cheng Yiling J. , Cowie Catherine C.
Published: January 2010

OBJECTIVE

We examined potential mediators of the reported association between diabetes and hearing impairment.

RESEARCH DESIGN AND METHODS

Data come from 1,508 participants, aged 40–69 years, who completed audiometric testing during 1999–2004 in the National Health and Nutrition Examination Survey (NHANES). We defined hearing impairment as the pure-tone average >25 decibels hearing level of pure-tone thresholds at low/mid (500, 1,000, and 2,000 Hz) and high (3,000, 4,000, 6,000, and 8,000 Hz) frequencies. Using logistic regression, we examined whether controlling for vascular or neuropathic conditions, cardiovascular risk factors, glycemia, or inflammation diminished the association between diabetes and hearing impairment.

RESULTS

Diabetes was associated with a 100% increased odds of low/mid-frequency hearing impairment (odds ratio 2.03 [95% CI 1.32–3.10]) and a 67% increased odds of high-frequency hearing impairment (1.67 [1.14–2.44]) in preliminary models after controlling for age, sex, race/ethnicity, education, smoking, and occupational noise exposure. Adjusting for peripheral neuropathy attenuated the association with low/mid-frequency hearing impairment (1.70 [1.02–2.82]). Adjusting for albuminuria and C-reactive protein attenuated the association with high-frequency hearing impairment (1.54 [1.02–2.32] and 1.50 [1.01–2.23], respectively). Diabetes was not associated with high-frequency hearing impairment after controlling for A1C (1.09 [0.60–1.99]) but remained associated with low/mid-frequency impairment. We found no evidence suggesting that our observed relationship between diabetes and hearing impairment is due to hypertension or dyslipidemia.

CONCLUSIONS

Mechanisms related to neuropathic or microvascular factors, inflammation, or hyperglycemia may be mediating the association of diabetes and hearing impairment.
Glucose Levels at the Site of Subcutaneous Insulin Administration and Their Relationship to Plasma Levels
Authors: Lindpointner Stefan , Korsatko Stefan , Köhler Gerd , Köhler Hans , Schaller Roland , Schaupp Lukas , Ellmerer Martin , Pieber Thomas R. , Regittnig Werner
Published: January 2010

OBJECTIVE

To examine insulin's effect on the tissue glucose concentration at the site of subcutaneous insulin administration.

RESEARCH DESIGN AND METHODS

A CMA-60 microdialysis (MD) catheter and a 24-gauge microperfusion (MP) catheter were inserted into the subcutaneous adipose tissue of fasting, healthy subjects (n = 5). Both catheters were perfused with regular human insulin (100 units/ml) over a 6-h period and used for glucose sampling and simultaneous administration of insulin at sequential rates of 0.33, 0.66, and 1.00 units/h (each rate was used for 2 h). Before and after the insulin delivery period, both catheters were perfused with an insulin-free solution (5% mannitol) for 2 h and used for glucose sampling only. Blood plasma glucose was clamped at euglycemic levels during insulin delivery.

RESULTS

Start of insulin delivery with MD and MP catheters resulted in a decline of the tissue glucose concentration and the tissue-to-plasma glucose ratio (TPR) for ∼60 min (P < 0.05). However, during the rest of the 6-h period of variable insulin delivery, tissue glucose concentration paralleled the plasma glucose concentration, and the TPR for MD and MP catheters remained unchanged at 83.2 ± 3.1 and 77.1 ± 4.8%, respectively. After subsequent switch to insulin-free perfusate, tissue glucose concentration and TPR increased slowly and reattained preinsulin delivery levels by the end of the experiments.

CONCLUSIONS

The results show the attainment of a stable TPR value at the site of insulin administration, thus indicating that insulin delivery and glucose sensing may be performed simultaneously at the same adipose tissue site.