bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Approach to Practical Pressure Transient Testing of Multiple Fracture Completed Horizontal Wells in Low Permeability Reservoirs
Authors: Volz Richard , Pinto Elvia , Soto Omar , Jones J. R. 
Published: January 2013

Abstract
The common well/completion configuration for most shale wells is a horizontal well with multiple transverse hydraulic fractures. This is also becoming a common choice for some tight gas reservoirs. Pressure transient testing of this well/completion configuration has not been considered practical or useful since the extraction of completion parameters (fracture conductivity and half-length) out of a recorded response requires an estimate of effective formation permeability. Obtaining an estimate of permeability directly from a buildup or drawdown test can only be done if data from the radial flow period which reflects this parameter is recorded. Unfortunately, for this well/completion configuration in a low permeability reservoir, this flow period occurs only after extremely long shut-in or flowing times.
In the first part of this paper, the possibility of exploiting some combination of the early time flow regimes present in pressure buildup data to overcome these difficulties is investigated. The paper outlines a specialized data collection and analysis approach that can allow data from relatively short (1 to 2 week) pressure buildups to be used to estimate completion parameters and effective flowing phase permeability. The approach relies on an analysis method which combines parameter estimates obtained from well-known early time flow regime equations with special typecurves that correlate derivative responses prior to fracture interference. The method is most reliable when the fracture radial flow period data is captured since this data is needed to place the measured response on the typecurves more uniquely. Possible methods which allow the collection or re-capture of this desirable early time data, despite large wellbore storage effects, are discussed.
The second part of this paper covers an application of the presented analysis method to pressure buildup data from a BP-operated well completed in the Woodford shale of the Arkoma Basin. This pressure buildup test was done as a field trial to prove the viability of the analysis approach presented here. This section includes a description of the test design/ execution and detailed analysis of the pressure buildup data. A reasonable interpretation of this Woodford shale data is consistent with relatively few, but long planar fractures draining nano-Darcy matrix. This interpretation of the stimulated rock volume is unexpected with implications on stimulation and well spacing strategies.
Multiscale Grid Design and Upscaling for a Full Field Tight Gas Reservoir Model on a Next Generation Simulator
Authors: King M. J. , Abacioglu Y.. , Ballin P. R. , Sebastian H. M. , Du S.. , Zhou Y.. 
Published: January 2013

AbstractReservoir management and simulation of tight gas reservoirs pose several interesting technical challenges. Accurate simulation estimates of the effectiveness of multi-stage fracturing, well rates, the interaction between multiple fractures, and between the reservoir and fractures requires high resolution gridding near the well. These predictions have been achieved in the past through the design of LGR (Local Grid Refinement) grids, or through the use of fractured well indices or cell permeabilities. The latter techniques are based upon steady state concepts and are less able to resolve well rate transients compared to the use of LGR grids.Decisions on well counts, spacing, and timing also depend upon the interaction between wells. These simulations face specific challenges due to the geology of these reservoirs: in addition to the permeability being low, the connectivity of these reservoirs is intermittent due to the three dimensional spatial patterns of sand deposition and subsequent diagenesis. If these reservoir models are over-averaged or not carefully upscaled, the barriers between sands and internal heterogeneity will be lost, leading to far too optimistic estimates of lateral continuity and under-estimates of infill requirements. The need for accurate flow simulation of these systems has led to the development of spatially adaptive upscaling techniques that honor the vertical discontinuities of the sands in the design of the coarsened simulation grid and which also preserves the heterogeneity within sands.In the current study, these two approaches have been combined, providing a model with both high resolution and computational efficiency. Starting with a high resolution 3D geologic model, the simulation grid is designed using refinement at the fractured wells, and successively coarsened away from the well, leading to an unstructured numerical problem. Away from the wells, the vertical coarsening utilizes the "pillar-based" adaptive coarsening of Zhou and King, 2011. Simulation is performed using a next generation unstructured commercial simulator. We will report upon the performance of the different techniques in terms of accuracy, computational efficiency, and how they are impacted by different implementations of the multiscale simulation grid design.
Post-Stimulation Fluid Recovery, Every Drop Counts: Case Histories from Saudi Arabia
Authors: Leal J. A. , Duarte J.. , Al-Ghurairi F.. , Izquierdo G. A. , Soriano J.. 
Published: January 2013

Abstract
Saudi Aramco, while developing the carbonate Khuff formation sought to continue increasing gas reserves for the Kingdom of Saudi Arabia. A recent optimization initiative was developed to tailor acid-fracturing fluid blends, including a nonionic microemulsion surfactant (ME), to reduce surface tension and modify the contact angle. This initiative resulted in reduced water saturation, higher load recovery, and improved relative permeability to gas, producing the wells back in record time. In recent years, the use of ME in hydraulic fracturing operations has been documented (especially in tight-gas formations) as a key variable to further improve production and increase reserves. These studies, based on both lab research and field data, have shown that ME enhances core permeability to gas and fluid recovery. Particularly for this operator, the use of ME reduced well cleanup time on average by 50%, while also reducing the environmental impact, indirect costs, and increasing cost savings in general.
This paper presents the learning curve with respect to the use of ME, including laboratory fluid screening, surfactant selection, and optimization of acid blends, including corrosion, volume optimization, and lessons learned about field implementation. Additionally, case histories are presented. Evaluation of well flowback and productivity analysis is also included for different permeability scenarios, demonstrating how the use of ME helps speed the cleanup of injected fluids. This evaluation has been useful for selecting the optimum surfactant concentration as a function of reservoir permeability and pressure. Benefits with respect to time optimization and safety are also included based on analysis of actual job data. Because of the benefits obtained, the use of ME is being extended to other field operations, such as well killing, coiled tubing (CT) well interventions, and fluid blends improvement (e.g., inhibited water), which is extensively used in in Saudi Arabia matrix acidizing jobs and proppant fracturing.
A Rigorous Method to Calculate the Rising Speed of Gas Kick
Authors: Ling Kegang , He Jun , Shen Zheng 
Published: January 2013

AbstractThe rising speed of gas kick is an important parameter in well control operation. The position of the gas kick dictates the pressure at the casing shoe, which is usually the weakest point in the openhole section, and the wellhead pressure, which is one of the key factors affecting the blowout preventer and choke folder. In this research we derived a rigorous model to estimate the rising speed of gas kick. Starting from the force analysis and mass conservation we developed the equation to calculate the forces exerting on the gas kick. With the mass of the gas kick the rising speed of the gas kick is calculated. The effect of wellbore temperature profile on the rising of the gas kick is taken into account in the derivation.Before the development of this model, the estimation of gas kick position is commonly based on experience. In most cases the experience alone is not good enough in well control. The proposed model provides a new approach with solid theoretical base to characterize the rising of gas kick in the hole. With that the whole process of the well control becomes simple and drilling engineers can control the well comfortably. The method can be combined with engineers experience to predict the downhole situation, shut-in casing pressure, and mud rate as functions of position of gas kick. Any deviation from the forecast indicates accidents or downhole problems. Therefore the proposed model is a valuable tool to diagnose the problems in well control.
Formation Breakdown Prediction for the Implementation of Hydraulic Fracturing on a HPHT Tight Gas Reservoir in Oman
Authors: Chavez Juan , Mjeni Rifaat , Briner Andreas 
Published: January 2013

Abstract
The increased global demand for new hydrocarbon resources leads to the exploration in more challenging environments such as shale gas, tight gas and coalbed methane, where hydraulic fracturing is the key technology to unlock the development of these unconventional resources.
In Oman, the challenges imposed by HPHT tight gas formations takes the implementation of hydraulic fracturing to the limits imposed not only by the available fracture technology but by the integrity of the completion components. These challenges increase when stress regime variations are strongly influenced by tectonics. Understanding and predicting the breakdown pressure profile (BDP), and its variability across the target zone, is fundamental for the successful implementation of hydraulic fracturing on tight gas formations.
This paper presents the comprehensive work performed for the integration of log derived data with laboratory rock characterization and field observations, leading to the definition of a BDP prediction methodology for tectonically stressed tight gas formations. Key aspects used as integral part of the methodology of the data acquisition and integration are discussed in detail, including the correlations defined between the BDP, formation injectivity variations and tectonics.
It also discusses how understanding the variations of BDP across selected intervals provides essential information to assess the identification of fracture initiation zones, perforations and hydraulic fracture strategies as well as completion design requirements, leading this to support the successful implementation of hydraulic fractures and further field development.
Calibration of Static Reservoir Models with Dynamic Data for Efficient Tight-Gas Field Development (Wyoming, US)
Authors: Merletti German D. , Pour Rohollah A. , Spain David R. 
Published: January 2013

Abstract
The Wamsutter field is located in south-central Wyoming within the eastern part of the Greater Green River basin. The field covers 1,620 square miles and includes more than 8,500 wells; it produces approximately 450 million cubic ft of gas a day. The Almond formation, which accounts for approximately 85% of the produced gas, was deposited in shallow marine parasequences characterized by strandplain, deltaic, or barrier island complexes and their non-marine counterparts. The upper interval, which was produced extensively, contains the thickest, most laterally continuous and best rock quality. Most of the remaining field development potential remains in sections characterized by thinner and discontinuous facies. In addition to the larger stratigraphic uncertainty, poorer rock quality makes permeability interpretation in uncored wells quite challenging.
We tackle reservoir uncertainty by taking gross depositional interpretation and superimposing gas effective permeability models that honor dynamic measurements. This paper describes our efforts to produce core-calibrated, log-derived, effective permeability models that match zonal contribution from production logging and initial production indices.
The critical steps in the petrophysical workflow are related to the interpretation of the log-derived absolute permeability and core-derived gas relative permeability. Log-derived absolute permeability was addressed by evaluating alternative stochastic (neural network-based) and deterministic models on wireline logs. Core-derived gas relative permeability was tackled by modeling unsteady, pulse decay-type measurements along with capillary pressure tests by rock type.
Alternative gas effective permeability models are integrated over perforated intervals (KegH) and compared to actual reservoir performance. The model exhibiting the best correlation with dynamic data is superimposed on gross depositional maps.
We discuss the assumptions and limitations of the various measurements that make up petrophysical workflows in tight-gas sands as well as their contribution to the location of infill and step-out opportunities.
Maintaining Horizontal Well Stability During Shale Gas Development
Authors: Shen Z.. , Ling Kegang 
Published: January 2013

Abstract
Along with the development of unconventional resource, an increasing number of researches and field operations have been focusing on horizontal shale gas well. The most crucial element of a horizontal well is to enlarge the drainage area, subsequently enhance the well productivity. The technique of hydraulic fracturing has been accepted as an industry standard in developing shale gas play. Therefore, the casing-cement-shale system in the horizontal well should be able to survive from any potential variation of temperature and pressure during well stimulations. The current horizontal well design for casing burst resistance and collapse resistance have been improved by some researchers. Little research can be found to consider the mechanical behavior of shale during the development of a horizontal shale gas well.
This paper focuses on the instability of shale behind the casing and cement in a horizontal shale gas well. The variation of Von-Mise stress with time resulting from the wellbore flowing fluid in the horizontal well is predicted. The proposed model also quantitatively elaborates the difference of temperature distribution in horizontal shale cased hole and open hole. Well stimulation fluid with lower temperature is found to increase the risk of failure in the horizontal shale well. With the model, the down-hole instability of shale gas play in horizontal wells can be evaluated confidently.
Hydraulic Fracturing Critical Design Parameters in Unconventional Reservoirs
Authors: Saldungaray Pedro , Palisch Terry , Shelley Robert 
Published: January 2013

AbstractHorizontal well drilling and hydraulic fracturing have become the enabling technologies for unconventional reservoir development. From tight gas, to oil and gas-producing shales and coal bed methane, all these resources rely on hydraulic fracturing for its commercial viability. The primary goal of the completion in these ultra-low permeability formations is to provide a conductive path to contact as much rock as possible, through the use of multistage hydraulic fractures along a horizontal lateral. Reservoir contact is optimized by defining the extent of the lateral length, the number of stages to be placed in the lateral, the fracture placement technique and job size. Fracture conductivity is determined by the proppant type and size, fracturing fluid system as well as the placement technique.While most parameters are considered in great detail in the completion design, the fracture conductivity receives lesser attention. On one side many feel that in extremely low permeability formations hydraulic fractures act as ‘infinitely conductive features’, even with minimal conductivity. On another side many factors that affect the effective conductivity acting in the hydraulic fracture are poorly understood or overlooked. This can lead to a disappointing outcome with wells producing below the reservoir potential.This paper presents a technique to assess the realistic fracture conductivity at downhole conditions, describe the relationship between conductivity and productivity and its economic implications in proppant selection. The effects of transverse fractures, low areal proppant concentration and flow dynamics, are also considered among other variables.Fracture modeling and actual field results will be presented to illustrate the optimization process. The case histories included in the paper show the successful implementation of this method in shale gas and liquids rich formations.
Sale of Private Equity–Owned Physician Practices and Physician Turnover
Authors: Berquist Victoria , Klarnet Lev , Dafny Leemore 
Published: February 2025

ImportancePrivate equity (PE) acquisition of physician practices is increasing, with owners targeting sales, or exits, in 3 to 7 years. Little is known about the association of exit with physician retention and subsequent employment.ObjectiveTo examine whether PE exit of physician practices is associated with changes in physician retention and subsequent choice of practice size.Design, Setting, and ParticipantsUsing data from the Centers for Medicare &amp;amp; Medicaid Services Doctors and Clinicians National Downloadable File from December 31, 2014, to December 31, 2020, this case-control study compared employment changes for physicians at PE-exiting practices sold between January 1, 2016, and December 31, 2018 (treatment group), with employment changes for matched control physicians in practices not sold by PE owners but with the same specialty, hospital referral region, practice size, and time period. Physicians billing fee-for-service Medicare during the study period were eligible for inclusion. A difference-in-differences design was used to compare retention between the treatment and control groups in the 2 years before and after exit using a multinomial logit model that adjusted for physician decade of graduation. Data were analyzed from August 1, 2023, to November 9, 2024.ExposureExit of a PE-owned physician practice.Main Outcomes and MeasuresPhysician employment outcomes included staying (continuing to bill through the initial practice), working elsewhere (only billing through other practices), and retirement (no longer billing). Whether a physician left to a join large (&amp;gt;120-physician) practice was also evaluated.ResultsOf the 1215 physicians included in the analysis (405 at 70 PE-exiting practices and 810 matched controls; 814 [67.0%] male and 401 (33.0%) were female. Physicians in all PE-exiting practices were typically in practices of more than 20 physicians (471 [65.2%]) and often in the South (373 [51.7%]). Dermatology was the leading specialty (216 [29.9%]), followed by family medicine (94 [13.0%]). Physicians employed in PE-exiting practices were 16.5 (95% CI, 10.6-22.3) percentage points less likely to continue working in that practice 2 years after exit compared with matched controls. There was no significant change in the probability of retirement (0 percentage points; 95% CI, −4.1 to 4.0). Physicians in PE-exiting practices were 10.1 (95% CI, 6.5 to 13.7) percentage points likelier than matched controls to join a large practice of more than 120 physicians.Conclusions and RelevanceIn this case-control study, PE exit was followed by an increase in physician turnover and subsequent employment at a large (&amp;gt;120-physician) practice relative to matched controls, notwithstanding similar turnover rates between these physicians and matched controls prior to exit. The increase in physician turnover and consolidation following PE exits has important implications for patients, physicians, investors, and physician markets.
Broadening the Healthy Aging Paradigm: Inclusion of Gestation, Development, and Reproductive Health
Authors: Yao Lan , Eikelboom John , Macnab Andrew , Yu Zhuo , Cao Yanhong , Wei Wei , Sun Shuqiu , Khalil Asma , Cho William C. , Qamar Farah Naz , Kremsner Peter , Oliu‐Barton Miquel , Wang Lishi , Sisa Ivan , Marks Florian , Wang Cong‐Yi , Graff J. Carolyn , Howard Scott C. , Gu Tianshu , Maida Marcello , Prochownik Edward V , Mashe Tapfumanei , Fly Alyce D , Hui Yang , Maier Andrea B. , Aleya Sami , Sun Dianjun , Wang Gang , Bischof Evelyne Yehudit , Aleya Lotfi , Gu Weikuan 
Published: February 2025

AbstractThe prevailing focus of lifespan health research has predominantly centered on “healthy aging”. This oversight may hinder the understanding of health across the lifespan, as disorders in earlier stages can substantially impact overall health and longevity. Aging, conceptually, begins at gestation. The trajectory of an individual's health is influenced from the earliest stages of life, where adverse conditions can set a foundation for lifelong health challenges. For example, suboptimal conditions during gestation leading to premature birth can predispose individuals to various health issues later in life. Additionally, precocious puberty defined as the onset of sexual maturity before eight years of age or early menopause—occurring before 50 years of age requires medical intervention and is indicative of atypical aging processes. To address these critical gaps in lifespan health research, the expansion of medical lexicons and research categorizations is advocated to include “healthy gestation,” “healthy development,” and “healthy reproduction” alongside “healthy aging.” This broader terminology will enable a more comprehensive investigation of disorders at all life stages. An integrative approach underscores the interconnectedness of all life stages and the continuous nature of aging, advocating for a seamless continuum in health research and interventions from gestation through late adulthood.
Mechanical Properties and Failure Mechanisms of Carbon Fiber/Resin Composites with Hot Press, Single‐Vacuum‐Bag, and Double‐Vacuum‐Bag Processes
Authors: Ren Liangliang , Zhang Deyuan 
Published: February 2025

In order to compare the mechanical properties of materials, acquire the crack propagation law and failure mode under different processes of carbon fiber/resin composites, the hot press process, double‐vacuum‐bag (DVB) process, and single‐vacuum‐bag (SVB) process were used to manufacture laminates in this paper, the void content and void morphology of the composite materials were observed by ultrasonic C‐scan, optical microscope, and scanning electron microscope. Four different types of mechanical tests were carried out: tensile, compressive, bending, and short‐beam shear tests, and the fracture morphology of the specimens was observed and analyzed. The failure mechanisms of the materials under different processes were explored based on the stress analysis. It is found that in the materials manufactured by SVB process, voids can induce stress concentration effect, reduce the stress area and interlayer bonding force, and cracks are more prone to initiate and propagate around voids. These are all factors contributing to the reduction of bearing capacity and accelerating the failure process in the material. The void contents of laminates manufactured by DVB process and hot press process are extremely low, it is difficult for cracks to propagate within the material, and the composites can maintain excellent mechanical properties.