bluuebunny/crossref_metadata_2025 huggingface dataset:
The Relationship Between Neighborhood Socioeconomic Characteristics and Physical Inactivity Among Adolescents Living in Boston, Massachusetts
Authors: Pabayo Roman , Molnar Beth E. , Cradock Angie , Kawachi Ichiro
Published: October 2014

Objectives. We sought to determine whether the socioeconomic environment was associated with no participation in physical activity among adolescents in Boston, Massachusetts.

Methods. We used cross-sectional data from 1878 urban adolescents living in 38 neighborhoods who participated in the 2008 Boston Youth Survey, a biennial survey of high school students (aged 14–19 years). We used multilevel multiple regression models to determine the association between neighborhood-level exposures of economic deprivation, social fragmentation, social cohesion, danger and disorder, and students’ reports of no participation in physical activity in the previous week.

Results. High social fragmentation within the residential neighborhood was associated with an increased likelihood of being inactive (odds ratio = 1.53; 95% confidence interval = 1.14, 2.05). No other neighborhood exposures were associated with physical inactivity.

Conclusions. Social fragmentation might be an important correlate of physical inactivity among youths living in urban settings. Interventions might be needed to assist youths living in unstable neighborhoods to be physically active.
Clustering of Midlife Lifestyle Behaviors and Subsequent Cognitive Function: A Longitudinal Study
Authors: Kesse-Guyot Emmanuelle , Andreeva Valentina A. , Lassale Camille , Hercberg Serge , Galan Pilar
Published: October 2014

Objectives. We examined the association between individual and clustered lifestyle behaviors in middle age and later in cognitive functioning.

Methods. Middle-aged participants (n = 2430) in the Supplémentation en Vitamines et Minéraux Antioxydant study self-reported their low physical activity, sedentary behavior, alcohol use, smoking, low fruit and vegetable consumption, and low fish consumption. We assessed cognition 13 years later via 6 neuropsychological tests. After standardization, we summed the scores for a composite cognitive measure. We estimated executive functioning and verbal memory scores using principal component analysis. We estimated the mean differences (95% confidence intervals [CIs]) in cognitive performance by the number of unhealthy behaviors using analysis of covariance. We identified latent unhealthy behavior factor via structural equation modeling.

Results. Global cognitive function and verbal memory were linearly, negatively associated with the number of unhealthy behaviors: adjusted mean differences = −0.36 (95% CI = −0.69, −0.03) and −0.46 (95% CI = −0.80, −0.11), respectively, per unit increase in the number of unhealthy behaviors. The latent unhealthy behavior factor with low fruit and vegetable consumption and low physical activity as main contributors was associated with reduced verbal memory (RMSEA = 0.02; CFI = 0.96; P = .004). No association was found with executive functioning.

Conclusions. Comprehensive public health strategies promoting healthy lifestyles might help deter cognitive aging.
The Return of the Pholela Experiment: Medical History and Primary Health Care in Post-Apartheid South Africa
Authors: Phillips Howard
Published: October 2014

I examine why South Africa’s pioneering Pholela model of primary health care, dating from the 1940s, held such appeal for the country’s new policymakers after 1994, and why those policymakers have failed to make it the basis of an effective public health care system since then. In the 1940s, the innovative Pholela experiment had served as such a model, to be replicated gradually throughout the country until a new health care system in its image was finally in place. However, this vision was dashed by the hostility of the mainstream medical profession and, after 1948, even more so by the new apartheid government, causing the idea to wither and become no more than a vanishing memory. In the 1990s, the model resurfaced as part of the country’s transition to democracy, eliciting great enthusiasm among a new generation of health policymakers. I conclude by looking at the fate to date of this second coming of the Pholela experiment.
Risk Factors for HCV Infection Among Young Adults in Rural New York Who Inject Prescription Opioid Analgesics
Authors: Zibbell Jon E. , Hart-Malloy Rachel , Barry John , Fan Lillian , Flanigan Colleen
Published: October 2014

Objectives. We investigated a cluster of new hepatitis C cases in rural New York among a cohort of young people who inject drugs (PWID) and misuse prescription opioid analgesics (POA).

Methods. We recruited a purposive sample of PWID from Cortland County for an in-person survey and HCV rapid antibody test (March–July 2012). We examined sociodemographics, drugs currently injected, and lifetime and recent injection behaviors to ascertain associations with HCV antibody (anti-HCV) positivity.

Results. Of 123 PWID, 76 (61.8%) were younger than 30 years, and 100 (81.3%) received HCV rapid testing. Of those tested, 34 (34.0%) were positive. Participants who reported injecting POA in the past 12 months were 5 times more likely to be anti-HCV positive than those who injected drugs other than POA, and participants who reported sharing injection equipment in the past 12 months were roughly 4 times more likely to be anti-HCV positive than those who did not.

Conclusions. Our analysis suggests people injecting POA may be at higher risk for HCV infection than people who inject heroin or other drugs but not POA.
Moving Beyond Misuse and Diversion: The Urgent Need to Consider the Role of Iatrogenic Addiction in the Current Opioid Epidemic
Authors: Beauchamp Gillian A. , Winstanley Erin L. , Ryan Shawn A. , Lyons Michael S.
Published: October 2014

An epidemic of drug overdose deaths has led to calls for programs and policies to limit misuse and diversion of opioid medications. Any parallel call to consider the risk of iatrogenic addiction when treating pain has been muted in comparison.

We have moved beyond questions of nonmedical use, abuse, and diversion to highlight the role of prescription opioids in causing addiction even when prescribed and used appropriately.

Unfortunately, current evidence is insufficient, and a rapid expansion of longitudinal research is urgently needed to guide clinicians in balancing the need for opioids with the risk of adverse consequences. Meanwhile, medical education should place greater emphasis on the abuse liability of prescription opioids, and providers should endeavor to attenuate risk when possible.
Using Research Evidence to Reframe the Policy Debate Around Mental Illness and Guns: Process and Recommendations
Authors: McGinty Emma E. , Frattaroli Shannon , Appelbaum Paul S. , Bonnie Richard J. , Grilley Anna , Horwitz Joshua , Swanson Jeffrey W. , Webster Daniel W.
Published: October 2014

Recent mass shootings have prompted a national dialogue around mental illness and gun policy. To advance an evidence-informed policy agenda on this controversial issue, we formed a consortium of national gun violence prevention and mental health experts. The consortium agreed on a guiding principle for future policy recommendations: restricting firearm access on the basis of certain dangerous behaviors is supported by the evidence; restricting access on the basis of mental illness diagnoses is not. We describe the group’s process and recommendations.
A Systematic Review of the Epidemiology of Nonfatal Strangulation, a Human Rights and Health Concern
Authors: Sorenson Susan B. , Joshi Manisha , Sivitz Elizabeth
Published: October 2014

We reviewed the literature on the epidemiology of nonfatal strangulation (also, albeit incorrectly, called choking) by an intimate partner.

We searched 6 electronic databases to identify cross-sectional, primary research studies from 1960 to 2014 that reported national prevalence estimates of nonfatal strangulation by an intimate partner among community-residing adults. Of 7260 identified references, 23 articles based on 11 self-reported surveys in 9 countries met the inclusion criteria. The percentage of women who reported ever having been strangled by an intimate partner ranged from 3.0% to 9.7%; past-year prevalence ranged from 0.4% to 2.4%, with 1.0% being typical.

Although many epidemiological surveys inquire about strangulation, evidence regarding its prevalence is scarce. Modifying or adding a question to ongoing national surveys, particularly the Demographic and Health Surveys, would remedy the lack of data for low- and middle-income countries. In addition, when questions about strangulation are asked, findings should be reported rather than only combined with other questions to form broader categories (e.g., severe violence). Such action is merited because of the multiple negative short- and long-term sequelae of strangulation.
The Ultimate Sucker-Rod String Design Procedure
Authors: Takacs Gabor , Gajda Mihaly
Published: October 2014

A properly designed sucker-rod string should provide failure-free pumping operations for an extended period. Improper design of rod tapers can lead to early mechanical failures (rod breaks) with a complete termination of pumping action and an inevitable loss of production. Because of its prime importance in sucker-rod pumping technology several rod string design procedures based on different assumptions were developed in the past. Since most sucker rod breaks are fatigue failures the mechanical design of sucker-rod string must consider the cyclic nature of rod loading and the appropriate fatigue endurance limit of the rod material. This is why most string designs utilize the modified Goodman diagram for calculating the lengths of rod tapers.

Available sucker-rod string design models calculate rod taper lengths that ensure proper operation without premature fatigue failures. Their common design problems are (a) defining the principle of taper length determination, and (b) calculating the true mechanical stresses along the string. The universally accepted principle of taper length calculations is to provide the same level of safety against fatigue failures in each taper section. Mechanical loads and stresses, on the other hand, are usually found in most of the design procedures from very approximate formulas. These loads, therefore, can greatly deviate from the true mechanical loads that would be measured in the rod string run in the well. The paper details the main features of available rod string designs and discusses their main characteristics; it provides a thorough comparison of designs involving the calculation of loads and stresses predicted from the solution of the damped wave equation. Using a predictive analysis program rod stresses are calculated that, plotted on the modified Goodman diagram, provide a proper comparison of the merits of the different rod string design methods.

Rod strings designed by available design procedures usually do not have identical safety included in the different tapers. This is due to the improper calculation of rod string loads that form the basis of calculating rod taper percentages. Based on the evaluation of the different available rod string designs the paper introduces a novel procedure that estimates rod loads from the predictive solution of the damped wave equation during the design process. Since loads calculated that way simulate actual loads very accurately, the most important limitation of previous rod string design procedures is eliminated. Strings designed using the proposed model, therefore, will have identical safeties against fatigue failures in each taper; the new design model provides the ultimate safety over previous designs.
Practical Application of Variable Rate / Variable Pressure Drop Decline Curve Analysis: Valdemar Lower Cretaceous Case History
Authors: Navarro J. M. , de Heer M. A.
Published: October 2014

Application of conventional decline curve analysis following Arps' method is limited to situations where flowing bottom-hole pressure is constant. This paper describes the application of Blasingame decline curve analysis in a low permeability reservoir where flowing bottom-hole pressures are reduced in frequent and managed steps.

The Valdemar Lower Cretaceous Field is a low effective permeability (from 0.1 to 1 mD) chalk reservoir developed offshore in the Danish North Sea through long horizontal wells (horizontal sections of approximately 10,000 ft) with up to 16 sand-propped fractures.

Pressure drawdown in Valdemar wells is managed by controlled lowering of the flowing bottom-hole pressure over time in order to avoid destabilization of the formation and well failure due to chalk production. These changes in operating conditions, in addition to reservoir complexity and challenging architecture of the wells make conventional methods (simulation, Arps' decline curve analysis and rate transient analysis) for production forecasting and well performance analysis either not adequate or difficult to implement. These issues have been resolved by applying advanced decline curve analysis to the variable rate / variable pressure drop theory.

Application of the Blasingame Theory for the Valdemar Lower Cretaceous Field using available commercial software is complicated as it requires input parameters which are not very well known such as fracture half-length, fracture conductivity and number of producing fractures. In addition, uncertainty in fluid and reservoir properties can make the task even more challenging, since a non-unique history match often results with subsequent predictions outside a reasonable range.

This paper presents a clear step by step, performance-based methodology of how to apply the Blasingame Theory to decline curve analysis. The methodology does not depend on detailed knowledge of well and fracture dimensions and it only requires the initial reservoir pressure, historical oil rates and flowing bottom-hole pressures to be known for production forecasting. This paper also presents the practical application to the Valdemar Lower Cretaceous Field.

This methodology has been demonstrated to work in the Valdemar Lower Cretaceous Field and it is currently the key tool used to evaluate well performance and to estimate reserves and resources associated with different production strategies (drawdown, gas lift, etc.).
A Friction Reducer: Self-Cleaning to Enhance Conductivity for Hydraulic Fracturing
Authors: Chung HsinChen , Hu Yantao T. , Ye Xiangnan , Maxey Jason E.
Published: October 2014

Hydraulic fracturing often involves the injection of large amounts of water at high rates into the formation to create fractures. Typically, friction reducers (FRs) are added to the water to reduce pipe friction caused by turbulence, with polyacrylamide-based (PAM-based) polymers being the most common FRs. However, these polymers are difficult to break because of their high molecular weight and long polymer chains. As such, one common issue with the use of FRs for hydraulic fracturing is fracture and formation damages, which can significantly reduce production.

A new technology featuring a self-cleaning FR has been developed to help minimize formation and propped fracture damage as well as enhance early and long-term flowback. This new FR exhibits a unique self-contraction property. With the addition of minimal to no breaker, its viscosity can decrease to water-like levels when exposed to high temperatures. Furthermore, the contracted polymer is small enough to pass through the pore throats, helping minimize formation and fracture damage.

This paper presents laboratory data to illustrate this unique self-contraction property and its benefits. Formation and fracture damage of this new FR on tight sandstones/sandpack is investigated using the regained permeability and conductivity tests. Field trials were conducted successfully in the Marcellus shale. All results indicate that this new FR has superior cleanup and fracture conductivity; additionally, it causes less formation damage than traditional FRs.
Reservoir Model Maturation and Assisted History Matching Based on Production and 4D Seismic Data
Authors: Joosten Gerard , Altintas Asli , van Essen Gijs , van Doren Jorn , Gelderblom Paul , van den Hoek Paul , Foreste Kenny
Published: October 2014

History matching in reservoir modelling is done increasingly with the help of (semi-) automated computer techniques, such as design of experiments (DoE), Ensemble Kalman Filtering or the adjoint-based techniques. Although such techniques will lead to accelerated estimation of the values of reservoir model parameters, they will not, by themselves, solve the often occurring problem of conceptual reservoir model inadequacies (missing faults, unidentified aquifers, etc.).

Over the past years, we have developed a technique called "Model Maturation", where we use an adjoint-based history match to flag such inadequacies, and subsequently address those in an interdisciplinary dialogue (between reservoir engineer, geologist, petrophysicist, and geophysicist). Such a forced history match is not limited to production data, but can also include data from 4D seismic, saturation logs and RFT measurements. The "matured" reservoir model is subsequently subjected to a standard Assisted History Match (AHM) using, for example, DoE to optimize the values of the revised set of reservoir parameters.

In this paper, we present a number of field cases, out of more than twenty worldwide by now, where we have successfully applied abovementioned workflow, thereby significantly improving the reservoir models in question, which in turn has a direct impact on the business decisions depending on those models.
Retrofit Solids Control in Live Gas Wells
Authors: Biezen E. N. , Hoekstra L. , Gesterkamp S. , von der Heide S. , Welling R. F.
Published: October 2014

In a number of mature gas fields in the Southern North Sea there are several multilateral open-hole completions that have proven to give significant solids/pebble production problems. Since the onset of production six out of seven total multilateral open-hole gas wells had to be shut in because of solids plugging. Collapse of the open hole multi-lateral junction is assumed to be the root cause of these problems. Wells that were drilled later in field life equipped with a pre-drilled liner did not show this solids production problem. There was, however, no way (short of a full workover to recomplete the well) to retrofit a solids control measure of this type until now. A coiled tubing cleanout campaign was commissioned to restore productivity of these plugged gas wells. After the cleanouts perforated jointed pipes have been installed in the bottom of the existing completion as a solids production prevention mechanism. This was done under live well conditions, without having to resort to snubbing. A newly developed special pipe connector was used to build in this perforated pipe section using a combination of braided wire and coiled tubing. Cleanout and restoration of gas production was successful for four out of the total six plugged wells. In conclusion, new connector technology has been instrumental in retrofitting a means of subsurface solids control in live gas wells with openhole original completions.
Fracture Shadowing: Theory, Applications and Implications
Authors: Daneshy Ali
Published: October 2014

The fluid pressure causing the extension of a hydraulic fracture also compresses the adjacent formation, mainly in the direction perpendicular to the fracture face. If there is a closed-in passive fracture within the compressed region, this causes an increase in its fluid pressure. The magnitude of pressure increase is a function of the distance between the two fractures (passive and active), the net extension pressure in the active fracture, and the overlap area. This pressure increase is defined as fracture shadowing and has been used for estimation of different fracture parameters, including orientation and length.

This paper presents the mathematical background of fracture shadowing, including relationship between net extension pressure, distance between fractures, extent of each fracture, and volume of existing passive fracture system. Through actual field data, it shows that shadowing can be used as a very simple and cost effective tool for estimation of different fracture parameters. Shadowing in the same well is used to determine fracture growth pattern as well as a rough indicator of orientation. In offset wells, shadowing can provide estimation of fracture orientation, type, length, and in some cases conductivity.

Paper demonstrates and recommends use of fracture shadowing as a simple and inexpensive additional diagnostic tool for determination of fracturing parameters.
Engineered Perforating Charges Designed for Stimulation
Authors: Leal Jairo , Ghurari Fadel , Zbitowsky Ron , Duarte Jorge , Yaseen Ali , Derouen Brock , Soriano Eduardo
Published: October 2014

Hydraulic fracturing is recognized as a successful stimulation technique used to enhance recovery from reservoirs. Prediction of fracture initiation and propagation from wellbores is necessary for efficient hydraulic fracturing stimulation tasks. Perforating is key to the success of a hydraulic fracturing treatment; it provides a means of communication between the wellbore and reservoir. Additionally, in a fracture-stimulated reservoir, the perforations serve as fluid conduits between the fracture and wellbore.

Once the fracture is created, perforations provide the entrance to the fracture for the proppant. The perforation diameter must be sufficient to help prevent bridging because an accumulation of proppant can block the entrance hole. Inadequate perforations, low perforating efficiency, and variations in perforation entrance hole diameter can increase the effects of near wellbore (NWB) tortuosity and leave several holes that do not contribute to stimulation, causing uneven treatment distribution, increased formation breakdown pressure, and suboptimal completion—occasionally beyond the pressure capability of the surface equipment or design rating of the well.

A new class of shaped charges engineered to maximize hole diameter while maintaining a consistent exit hole diameter independent of well profile and/or gun eccentricity has recently been introduced for unconventional resources requiring stimulation. Designed for perforating before a hydraulic stimulation, these new charges can help reduce the probability of screenout during the fracturing process.

This paper describes the new charge technology in detail and addresses its successful deployment during fracturing of tight gas wells in Saudi Arabia. Specific examples are used to illustrate how the system facilitates prefracture evaluation, fracture initiation, and how fracture tortuosity and perforation friction entry values are decreased compared to previous perforating systems.
Designing and Implementing a Competency-Based Development Program for Iraqi Graduate Engineers
Authors: Saadawi Hisham , Al Sammarrai Wathik
Published: October 2014

A consortium made of PetroChina, Total and Petronas signed an agreement with the Iraqi government to develop the giant Helfaya field, Iraq. In 2012, PetroChina recruited 21fresh Iraqi graduates of different engineering disciplines to integrate them into the Company operations. They were graduates from the various local universities and colleges across Iraq.

It was evident that a traditional training program similar to what is used by many companies in the oil industry would not be suitable for the Iraqi graduates. A competency-based development program was specifically designed for Halfaya field operations and the needs of the newly recruited graduates.

This paper describes the approach adopted in designing this program, the key features of the program and the implementation experience.

Iraq has the world's second largest proven reserves of conventional crude oil after Saudi Arabia. While there are many publications on the technical aspects of the Iraqi oil industry, there is very little published on the development of Iraqi professional work force. This paper is a contribution towards bridging this gap. It provides a case study on how to design and implement a competency-based graduate development program tailor-made for Iraqi graduates.
Waterflooding Surveillance and Optimization for a Super-Giant Carbonate Reservoir
Authors: Wei Chenji , Li Yong , Song Benbiao , Zhou Jiasheng , Li Baozhu , Zhang Weimin
Published: October 2014

Waterflooding performance determines the recovery and life cycle of carbonate reservoirs. This paper presents a waterflooding surveillance and development plan optimization of a super-giant carbonate reservoir, which is a Cretaceous carbonate reservoir in Middle East, with OOIP of 4000 MM bbls.

This carbonate reservoir started to produce since 1970's without any energy supply, and the current reservoir pressure is just above the bubble point pressure. Therefore, water flooding project has been launched over the past 2 years. We presented a method to integrate the geology, production and injection data, PLT (Production Logging Test), saturation test, and pressure test. Based on the valuable data, we presented a comprehensive surveillance of the water flooding project and the careful evaluation about its effect. Then, based on the surveillance, reservoir simulation is conducted to optimize the pressure maintenance target, production rate, well pattern, well spacing etc. for different types of formation, and eventually an optimized development plan is proposed.

Workflow of waterflooding surveillance is established, and results and analysis for this field are shared. Important information such as the main flow direction of water and increased reservoir pressure are determined. Productions of several oil wells near the injectors are enhanced more than 45%, which indicates that the effect of waterflooding is significant. In addition, optimized parameters are obtained from reservoir simulation, and some interesting observations are found, such as that if we maintain the reservoir pressure just below the bubble point, the recovery is one of the best of the 6 scenarios. Furthermore, the optimized development plan increased more than 15% oil recovery compared with the base development strategy.

This study offers a comprehensive case study that supports engineers and geologists for better understanding the formation, monitoring the waterflooding process, and optimizing production plan on this carbonate.
Stick-Slip Detection and Friction Factor Testing Using Surface-Based Torque and Tension Measurements
Authors: Lai Stephen W. , Wood Mitch , Eddy Aaron , Holt Trevor , Bloom Matthew
Published: October 2014

Recently, there has been a strong push towards automation and the use of real-time models in the drilling industry. However, it has been recognized that these new methods require a drastic improvement in the quality of sensor data gathered at the rig. In this paper, we investigate how accurate measurement of drill pipe torque and tension at the surface can be used to diagnose downhole conditions.

A surface-based torque and tension sub was used to perform measurements while drilling several extended reach horizontal wells in the Dilly Creek area of the Horn River Basin. A filtered version of surface torque was used to calculate a stick-slip metric which was compared to stick-slip measurements using a downhole tool. The results show that there is reasonable correlation between surface and downhole metrics, but the correlation is highly dependent on torque filter stop frequency. A comparison is also performed between the hookload measured with a deadline sensor and the tension measurement from the surface sub. The results show a systematic discrepancy of approximately 5% that is likely due to sheave friction. A commercial torque and drag software package is used to show that values for casing friction factor may be underestimated if sheave friction is present but ignored in the analysis.
Controlling Extreme Fluid Loss During Workover Operations in Dual-Porosity Reservoirs with Hydraulically Induced Fractures
Authors: Delgado Eduardo , Crespo Freddy , Zabala Richard
Published: October 2014

Fluid losses during overbalanced well interventions particularly in depleted and under-pressured formations can become excessive in the presence of naturally occurring fractures, vugs, and caverns. Such features in combination with hydraulically induced fractures pose a set of issues that contribute heavily to the amount of fluid being lost into the formation. In this type of scenario it is not uncommon for the rate of fluid loss to exceed available pumping capabilities.

This paper highlights the successful design and implementation of a robust pill to control excessive completion fluid losses, minimize formation damage in dual-porosity reservoirs with hydraulically induced fractures, while contributing to improve injection profile. This treatment contains a low-viscosity, solids-free, relative permeability modifier system coupled with biodegradable natural cellulose fibers for lost circulation control during workover and drilling operations.

This system was applied to a cased-hole oil producer completed in the presence of natural and induced fractures (4500 psi, 15,500-ft TVD, and 270°F) in the Mirador, Barco, and Guadalupe formations in Colombia. This well was intended to be converted from a high-water cut producer into a gas injector to support field revitalization. Also, better access to the Barco and Guadalupe formations was desired to increase the injection profile. Excessive fluid losses during the workover made it impossible to carry out operations as planned. Ten pills of different conventional lost circulation materials (LCM) were implemented with no success. There was still a need to reduce losses below 10 bbl/hr to continue.

Two 50-bbl pills of the proposed treatment were spotted to the target zone. Losses were immediately decreased to 9.1 bbl/hr on the first attempt, enabling continuation of the interventions with no further non-productive time (NPT). After completion, the well was successfully cleaned-out with nitrogen through coiled tubing (CT), and after two months, efficient gas injection was started as planned with the desired injection profile and no signs of further damage.
A Semi-analytical Solution to the Transient Temperature Behavior along the Wellbore and Its Applications in Production Management
Authors: Xu Boyue , Wu Xingru , Gao Yonghai , Ling Kegang
Published: October 2014

Temperature measured from a permanent downhole gauge in a well after the well shut-in provides a unique perspective for surveillance and production management purposes. For example, in deepwater environment, production engineers need to know the temperature status of a shut-in well before it is being restarted since different temperature profiles along the wellbore may need very different restarting strategies for flowing assurance purposes. A number of "rule-of-thumb" or complicated numerical simulations are either not reliable or impractical.

This paper presents a semi-analytical model to estimate the temperature transient behavior after the well shut-in. The model is solved numerically through inverse Laplace transform and integration. This solution gives temperature distribution profile and history in any location along the radial direction for a given production time and shut-in duration. To make it more general for other wells, an empirical correlation is provided through regression on the calculated type curves. The difference between this semi-analytical solution with other previous efforts will be discussed.

The applications of the solution to this model are multiple folders. For example, we can use the solution to predict the temperature behavior after the well shut-in, which can be used for flow assurance purposes. Furthermore, matching the calculated temperature with the measured temperature at the same location will yield the well local heat transmissibility coefficient. Some field examples are provided to demonstrate these applications.
Integration of Principal-Component-Analysis and Streamline Information for the History Matching of Channelized Reservoirs
Authors: Chen C. , Gao G. , Honorio J. , Gelderblom P. , Jimenez E. , Jaakkola T.
Published: October 2014

Although Principal Component Analysis (PCA) has been widely applied to effectively reduce the number of parameters characterizing a reservoir, its disadvantages are well recognized by researchers. First, PCA may distort the probability distribution function (PDF) of the original model, especially for non-Gaussian properties such as facies indicator or permeability field of a fluvial reservoir. Second, it smears the boundaries between different facies. Therefore, the models reconstructed by PCA are generally unacceptable for geologists.

A workflow is proposed to seamlessly integrate Cumulative-Distribution-Function-based PCA (CDF-PCA) and streamline information for assisted-HM on a two-facies channelized reservoir. The CDF-PCA is developed to reconstruct reservoir models using only a few hundred of principal components. It inherits the advantage of PCA to capture the main features or trends of spatial correlations among properties, and more importantly, it can properly correct the smoothing effect of PCA. Integer variables such as facies indicators are regenerated by truncating their corresponding PCA results with thresholds that honor the fraction of each facies at first, and then real variables such as permeability and porosity are regenerated by mapping their corresponding PCA results to new values according to the CDF curves of different properties in different facies. Therefore, the models reconstructed by CDF-PCA preserve both geological (facies fraction) and geostatistical (non-Gaussian distribution with multi-peaks) characteristics of their original or prior models. Our preliminary results indicate that the history-matched model using the CDF-PCA alone may not satisfy the requirement of geologists, e.g., some channels may become disconnected during history-matching. Therefore, we propose a method of combining CDF-PCA together with streamline information. Because velocity of the tracer in the streamline provides connectivity information between injectors and producers, it enhances channel connectivity without over-correction on cell-based permeability during the process of history matching.

The CDF-PCA method is applied to a real-field case with three facies to quantify the quality of the models reconstructed. The history matching workflow is applied to a synthetic case. Our results show that the geological facies, reservoir properties, and production forecasts of models reconstructed with CDF-PCA are well consistent with those of the original models. The integrated HM workflow of CDF-PCA with streamline information generates reservoir models that honor production history with minimal compromise of geological realism.
Breathing a New Life for Kinabalu – A Showcase of Operatorship Handover, Field Rejuvenation and Operational Synergies for a Mature Oil Field in Malaysia
Authors: Othman Mohamad , Masoudi Rahim , Pilus Azmi
Published: October 2014

The Kinabalu oil field is located offshore Sabah, Malaysia was relinquished to PETRONAS after the expiry of the Production Sharing Contract (PSC) at the end of 2012 after 15 years in production. As common to other matured fields, Kinabalu was experiencing many sub-surface and operational challenges that need to be overcome in order to realize the field full potential. The challenge for PETRONAS as the host authority and resource owner is to select the new operator with proven field redevelopment and mature asset management expertise to take over the operatorship. The new operator should also have the mature field mindset and expected to maximize hydrocarbon recovery through major capital investment, reduce the production cost through operational efficiency and synergies and mature the upside potential. As the host authority it is imperative for PETRONAS to incentivize the operator to continue to identify opportunities to grow the asset through innovative Petroleum Arrangement.

The paper showcases, the successful collaboration efforts between the host authority, the operator and the partner to overcome various challenges to add value to this mature asset through smooth operatorship handover, field redevelopment plans and operational synergies between operators in the South Sabah region. The paper will highlight the role played by the host authority to incentivize and influence the operators to execute the field rejuvenation effort and to realize the potential of a mature field. The paper will discuss the key challenges in the planning and execution of fast track field development to rejuvenate the field and to increase the oil production from 7,000 bopd to 20,000 bopd. The paper will also discuss an integrated operating model to facilitate more efficient and effective utilization of existing and planned infrastructure, improve facilities uptime and reduce the overall operating and development costs for the mutual benefit of operators in the region.

The successful effort to breathe a new life to Kinabalu field marked a significant milestone for the Malaysian oil and gas industry. This is also the first time in the history of the Malaysia oil industry that the asset and the operatorship was transferred from one International Oil Company (IOC) to another IOC. A new innovative Petroleum Arrangement (PA) was adopted for the first time for the matured field PSC in Malaysia to incentivize the PSC operator to grow the asset. The results and lessons learned from the project are crucial in the other future field operatorship handover and mature field rejuvenation in Malaysia.
A Novel Way to Spot and Squeeze a Lost Circulation Cement Plug Using Managed Pressure Drilling Techniques in HP/HT Conditions: Case History from the Mediterranean Sea
Authors: Bhaisora Devesh , Waheed Arshad , Gawad Mohamed Abdel , Hollman Landon , Fayed Mohamed Idris , Mehdiyev Akshin , Geldof Wilco
Published: October 2014

Curing losses during drilling is a widely known and discussed topic. Losses are mainly cured by spotting a lost circulation pill from the mud company or by spotting and squeezing a lost circulation cement plug. Many papers have been published regarding the composition of lost circulation pills, which is considered one of the key success factors. However, the technique used to place these pills in a zone of interest also can be tricky and equally contributes to the success of the job.

In most cases, a cement plug is spotted using the traditional balanced plug method. However, in high-pressure/high-temperature (HP/HT) wells having a very narrow margin between pore pressure and fracture gradient, there is very little probability of spotting a balanced cement plug successfully under lost circulation conditions. In the above mentioned situation, spotting any cement plug becomes a critical application. The correct amount of annular pressure required during the spotting of the plug must be calculated precisely, as even minor differences in applied surface pressure can damage the downhole stability of the cement plug.

BG Egypt recently experienced complete losses, resulting in a loss of more than 1,000 bbl of oil-based mud (OBM) in the Miocene section while drilling a HP/HT well offshore in the Mediterranean Sea. The immediate loss in hydrostatic pressure reduced the equivalent mud weight (EMW) on bottom and required the response of the managed pressure drilling (MPD) system to apply sufficient annular pressure to control the well by spotting lost circulation material (LCM) pills and a cement plug at desired depths. This paper discusses the novel approach used to successfully spot and squeeze a LCM pill and cement plug in a HP/HT situation with a narrow pressure margin using an MPD system, which resulted in reduced mud losses, increased success of the LCM pill and cement plug setting, and reduced time required to fully manipulate the EMW on bottom.
In-Situ Wettability Utilizing Low Gradient Magnetic Resonance
Authors: Jebutu Segun , Li Weidong
Published: October 2014

Hydrocarbon recovery, production mechanisms and field development economics strongly rely on understanding the wetting characteristics of the in-situ reservoir fluids. In the Gulf of Mexico reservoir systems presented, we characterize and profile the occurrence of mixed wettability conditions. This paper presents a new approach to estimate wettability, utilizing low-gradient magnetic resonance technology. Core data, core flood experiments, advanced fluid sampling and dynamic temperature anomaly evaluations are integrated to investigate the pore-scale complex fluid distributions and connectivity of varying wettability systems.

Wettability is difficult to measure in-situ, however the interaction of the fluid and rock mineral surfaces have an apparent relaxation time that is influenced by the surface relaxation mechanism of magnetic resonance. Wettability can be measured in the laboratory through contact angle, atomic forces microscope imaging and Amott index measurements. These are scale-constrained and it is difficult to replicate original down-hole conditions for these measurements. The new approach enables direct wettability estimation at in-situ reservoir conditions.

A spin-lattice function is derived, which is directly related to the interfacial tension and surface wetting fluid properties. A wettability index is then computed from the function using a reference zone below the free water level. The results indicate mixed wetting characteristics in asphaltenes and heavy-to-solid hydrocarbon-bearing sections. Several other factors evaluated that may account for the wettability distribution include asphaltene content of oil, acid number of the oil, rock surface roughness estimated from grain size modeling, and paleo-diagenetic thermal and pressure history of the reservoir. A more significant challenge for production performance from mixed wet systems is the connectivity of the wetting phases that may aid or impair mobility of fluid displacement, which can now be characterized by a depth-continuous wettability. The early knowledge of the presence of mixed wet system allows for optimal development planning of future recovery methods.
Rigorous Modeling for Data Analysis towards Accurate Determination of Shale Gas-Permeability by Multiple-Repeated Pressure-Pulse Transmission Tests on Crushed Samples
Authors: Civan Faruk , Devegowda Deepak
Published: October 2014

Determination of the nanodarcy gas permeability and other parameters of shale by pressure-pulse transmission testing of core plugs, drill cuttings, and crushed samples is discussed. The methods available for interpretation of pressure-pulse decay tests are reviewed with emphasis on the difference between the intrinsic and apparent permeability. Improved formulation and analysis which honor the relevant physics of gas transport and interactions of flowing gas with the shale under the pore-proximity and elevated pressure conditions are presented. Modification of the shale and fluid properties under prevailing stress, and pore-size distribution, connectivity, and confinement conditions is shown to be important under any pressure conditions while the gas rarefaction and slippage effects diminish essentially at high pressures but become important at low pressures. The permeability and other parameters of shale samples are determined by numerical modeling and analysis of the pressure tests conducted under different conditions in order to accommodate for temporally and spatially variable conditions. Better design and analysis of experiments for simultaneous determination of several unknown parameters that impact transport calculations, including stress-deformation, adsorption, diffusion, and deviation from Darcy flow are described. The inherent limitations of the earlier methods which rely on the approximate analytical solutions of the simplified diffusivity equation based on the Darcy's law are delineated. It is pointed out that the permeability measured using a Darcy-type equation is the apparent permeability and not the intrinsic permeability. Thus, the primary reason for the contradictory values of permeability measured by application of the analytical models is explained by dependence of the permeability of shale to different testing conditions over which only different average permeability values can be obtained when applying the approximate analytical solutions obtained based on the assumption of a constant permeability value.
An Improved Complex Image Theory for Fast 3D Resistivity Modeling and Its Application to Geosteering in Unparallel Layers
Authors: Chen Jiefu , Yu Yao
Published: October 2014

Azimuthal resistivity logging-while-drilling (LWD) tools are widely used in geosteering because of their azimuthal sensitivity and depth of investigation compared to those of other LWD tools such as nuclear, acoustic, or gamma ray measurements. Compared to conventional resistivity tools, azimuthal resistivity LWD measurements can provide additional information including distance to bed interface, relative dip, and resistivity anisotropy. Because of the computing efficiency requirement, modeling and inversion of azimuthal resistivity LWD measurements are usually based on the 1D parallel layer model: i.e., all bed interfaces are infinitely large and parallel to each other. Clearly this 1D model assumption does not apply to some realistic situations such as when the tool is navigating in an unparallel layered formation, or approaching a fault.

3D full wave simulations such as finite difference or finite element methods can handle the complex cases, but they are generally too slow for real jobs, not to mention the inversion based on forward modeling. An approximation method called "complex image theory" was proposed for geophysical prospecting and recently introduced to well logging. This theory approximates electromagnetic wave reflection by an interface between local and adjacent beds as signal radiated from a virtual source with a complex distance from the observation point. The complex image theory can be several orders of magnitude more efficient than 3D simulations. However, it also has several limitations: This method only works in resistive beds with conductive shoulders, and measurement cannot be too close to bed interfaces. Those shortcomings greatly limit this method to more extensive applications.

An improved complex image theory is proposed here to tackle the aforementioned difficulties. This improved theory can handle finite-sized interfaces, any distance from the tool to a bed interface, and the scenarios where the source is in a conductive bed instead of a resistive one. An efficient and robust inversion scheme is also implemented based on the improved complex image theory. This proposed method can greatly facilitate formation evaluation and decision making of geosteering in complex scenarios. Synthetic data, laboratory experiments, and field jobs are shown here to demonstrate the effectiveness of this improved complex image theory.