bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterize Fracture Development Through Strain Rate Measurements by Distributed Acoustic Sensor DAS
Authors: Tang Jin , Zhu Ding 
Published: January 2022

Abstract
In multistage hydraulic fracturing treatments, the combination of extreme large-scale pumping (high rate and volume) and the high heterogeneity of the formation (because of large contact area) normally results in complex fracture growth that cannot be simply modeled with conventional fracture models. Lack of understanding of the fracturing mechanism makes it difficult to design and optimize hydraulic fracturing treatments. Many monitoring, testing and diagnosis technologies have been applied in the field to describe hydraulic fracture development. Strain rate measured by distributed acoustic sensor (DAS) is one of the tools for fracture monitoring in complex completion scenarios. DAS measures far-field strain rate that can be of assistance for fracture characterization, cross-well fracture interference identification, and well stimulation efficiency evaluation. Many field applications have shown DAS responses on observation wells or surrounding producers when a well in the vicinity is fractured. Modeling and interpreting DAS strain rate responses can help quantitatively map fracture propagation.
In this work, a methodology is developed to generate the simulated strain-rate responds to assumed fracture systems. The physical domain contains a treated well that the generate strain variation in the domain because of fracturing, and an observation well that has fiber-optic sensor installed along it to measure the strain rate responses to the fracture propagation. Instead of using a complex fracture model to forward simulate fracture propagation, this work starts from a simple 2D fracture propagation model to provide hypothetical fracture geometries in a relatively reasonable and acceptable range for both single fracture case and multiple fracture case. Displacement discontinuity method (DDM) is formulated to simulate rock deformation and strain rate responds on fiber-optic sensors. At each time step, fracture propagation is first allowed, then stress, displacement and strain field are estimated as the fracture approaches to the observation well. Afterward, the strain rate is calculated as fracture growth to generate patterns as fracture approaching. Extended simulation is conducted to monitor fracture propagation and strain rate responses. The patterns of strain rate responses can be used to recognize fracture development.
Examples of strain rate responses for different fracturing conditions are presented in this paper. The relationship of injection rate distribution and strain rate responses is investigated to show the potential of using DAS measurements to diagnose multistage hydraulic fracturing treatments.
Comparison of Wormhole Profiles on Carbonate Rocks Using Emulsified and Single-Phase Retarded Acids
Authors: Aljuryyed Norah , Al Moajil Abdullah , Caliskan Sinan , Alghamdi Saeed 
Published: January 2022

Abstract
Acid retardation through emulsification is commonly used in reservoir stimulation operations, however, emulsified acid are viscous fluids, thus require additional equipment at field for preparation and pumping requirements. Mixture of HCl with organic acids and/or chemical retarders have been used developed to retard acid reaction with carbonate, however, lower dissolving power. Development of low viscosity and high dissolving retarded acid recipes (e.g., equivalent to 15-26 wt.% HCl) addresses the drawbacks of emulsified acids and HCl acid mixtures with weaker organic acids. The objective of this study is to compare wormhole profile generated as a result of injecting acids in Indian limestone cores using 28 wt.% emulsified acid and single-phase retarded acids at comparable dissolving power at 200 and 300°F. Coreflood analysis testing was conducted using Indiana limestone core plugs to assess the pore volume profile of retarded acid at temperatures of 200 and 300° F. This test is supported by Computed Tomography to evaluate the propagation behavior as a result of the fluid/rock reaction.
Wider wormholes were observed with 28 wt.% emulsified acid at 200°F when compared to test results conducted at 300°F. The optimum injection rate was 1 cm3/min at 200 and 300°F based on wormhole profile and examined flow rates. Generally, face-dissolution and wider wormholes were observed with emulsified acids, especially at 200°F. Narrower wormholes were formed as a result of injecting retarded acids into Indiana limestone cores compared to 28 wt.% emulsified acid. Breakthrough was not achieved with retarded acid recipe at 300°F and flow rates of 1 and 3 cm3/min, suggesting higher flow rates (e.g., &gt; 3 cm3/min) are required for the retarded acid to be more effective at 300°F.
Geomechanical Controls on Frac-Hits
Authors: Kumar Dharmendra , Ghassemi Ahmad 
Published: January 2022

Abstract
The communication among the horizontal wells or "frac-hits" issue have been reported in several field observations. These observations show that the "infill" well fractures could have a tendency to propagate towards the "parent" well depending on reservoir in-situ conditions and operational parameters. Drilling the horizontal wells in a "staggered" layout with both horizontal and vertical offset could be a mitigation strategy to prevent the "frac-hits" issue. In this study, we present a detailed geomechanical modeling and analysis of the proposed solution. For numerical modeling, we used our state-of-the-art fully coupled poroelastic model "GeoFrac-3D" which is based on the boundary element method for the rock matrix deformation/fracture propagation and the finite element method for the fracture fluid flow. The "GeoFrac-3D" simulator fully couples pore pressure to stresses and allows for dynamic modeling of production/injection and fracture propagation. The simulation results demonstrate that production from a "parent’ well causes a non-uniform reduction of the reservoir pore pressure around the production fractures, resulting in an anisotropic decrease of the reservoir total stresses, which could affect fracture propagation from the "infill" wells. We examine the optimal orientation and position of the "infill" well based on the numerical analysis to reduce the "frac-hits" issue in the horizontal well refracturing. The posibility of "frac-hits" can be reduced by optimizing the direction and locations of the "infill" wells, as well as re-pressurizing the "parent" well. The results suggest that arranging the horizontal wells in a "staggered" or "wine rack" arrangement decreases direct well interference and could increase the drainage volume.
Production Monitoring of Multilateral Wells by Quantum Marker Systems
Authors: Husein Nadir , Upadhye Vishwajit , Drobot Albina Viktorovna , Bolshakov Viacheslav Valeryevich , Buyanov Anton Vitalyevich 
Published: January 2022

Abstract
Reliable information about the inflow composition and distribution in a multilateral well is of great importance and an existing challenge in the oil and gas industry. In this paper, we present an innovative method for dynamic monitoring of inflow profile based on quantum marker technology in a multi-lateral well located in West Siberia.
Marker systems were placed in the well during the well reconstruction by horizontal side tracking with the parent borehole remaining in production. This way of reconstruction allows development of the reservoir drainage area with a lateral hole and bringing the oil reserves from the parent borehole into production, which results in an increased flow rate and improved oil recovery rate. Placement of marker systems into parent borehole and side-track for fluid distribution monitoring allows to evaluate the flow rate from every borehole and estimate the effectiveness of performed well reconstruction.
Marker systems are placed into the parent borehole as a downhole sub installed into the well completion string. For the side-track polymer-coated marked proppant was injected during hydraulic fracturing to place markers.
The developed method was reliably used for an accurate and fast determination of the inflow distribution in a multi-lateral well which allows more efficient field development and also enabled us to provide effective solutions for following challenges:
Providing tools for timely water cut diagnostics in multilateral wells and information for water shut-off method selection; Selecting the optimal well operating mode for effective field development and premature flooding prevention in one or both boreholes; Evaluating whether well construction was performed efficiently, and an increased production rate was achieved; Leading to a considerable economic savings in capital expenditure.
Relative Permeability Behavior of Oil- Water Systems in Wolfcamp and Eagle Ford Fractures
Authors: Guerra Dante , Arceneaux Deron , Zhu Ding , Hill A. D. 
Published: January 2022

Abstract
Presently, two-phase flow behavior through propped and unpropped fractures is poorly understood, and due to this fact, reservoir modeling using numerical simulation for the domain that contains fractures typically assumes straight-line relative permeability curves and zero capillary pressure in the fractures. However, there have been several studies demonstrating that both viscous and capillary dominated flow can be expected in fractured reservoirs, where non-linear fracture relative permeabilities must be used to accurately model these reservoirs. The objective of this study is to develop an understanding of the relative permeability of oil-water systems in fractures through experimental study.
The experimental measurements conducted in this study were done using downhole cores from the Wolfcamp and the Eagle Ford Shale formations. The cores were cut to 1.5-in diameter and 6-in length testing samples. The specimens are saw-cut to generate a fracture along each sample first, and then conditioned in the reservoir fluid at the reservoir temperature for a minimum of 30 days prior to any testing. Wolfcamp and Eagle Ford formation oil and reconstituted brine with and without surfactants are used as the test fluids. The measurements were recorded at effective fracture closure stress and reservoir temperature. Also, real-time measurements of density, pressure, and flow rate are recorded throughout the duration of each test. Fluid saturation within the fracture was calculated using the mass continuity equation. The oil-water relative permeability was measured using the steady-state method. All measurements were conducted at reservoir temperature and at representative effective fracture closure stress.
The data from the experimental measurements was analyzed using Darcy's law, and a clear relationship between relative permeability and saturation was observed. The calculated relative permeability curves closely follow the generalized Brooks-Corey correlation for oil-water systems. Furthermore, there was a significant difference in the relative permeability curves between the oil-water only systems and the oil-water surfactant systems.
The result of this study is useful for estimating the expected oil production more realistically. It also provides information about the effect of surfactants on oil-water relative permeability for optimal design of fracture fluids.
Modeling of Before Closure Zero Slope Pressure Derivative in a Diagnostic Fracture Injection Test DFIT
Authors: Liu Guoqing , Wang Jie , Ehlig-Economides Christine 
Published: January 2022

Abstract
Recent diagnostic fracture injection test (DFIT) data presented on a Bourdet log-log diagnostic plot showed derivative slope of 0 in the before closure (BC) portion of the DFIT response. Some works qualitatively describe it as radial flow. This behavior has not been quantitatively analyzed, modeled and matched. The present work disagrees with the hypothesis of radial flow and successfully matches the relatively flat trend in the Bourdet derivative with a model dominated by friction dissipation coupled with tip extension.
The flat trend in Bourdet derivative occurs shortly after shut-in during the before closure period. Because a flat derivative trend suggests diffusive radial flow, our first approach was to consider the possibility that an open crack at a layer interface stopped the fracture propagation and caused the apparent radial flow behavior observed in falloff data. However, a model that coupled pressure falloff from diffusive flow into a layer interface crack with pressure falloff from closure of a fracture that propagated up to the layer interface failed to reproduce the observed response. Subsequently, we discovered that existing models could match the data without considering the layer interface crack.
We found that data processing is very important to what is observed in derivative trends and can mislead the behavior diagnosis. We succeeded to match one field DFIT case showing an obvious early flat trend. The presence and dominance of geomechanics, coupled with diffusive flow, disqualify the description of the flat trend in Bourdet derivative as radial flow. Instead, flow friction coupled with tip extension can completely match the observed behavior. Based on our model, cases with a long flat trend have large magnitude near-wellbore tortuosity friction loss and relatively long tip extension distance. Further, we match the near wellbore tortuosity behavior with rate raised to a power lower than the usually assumed 0.5.
The significance of these analyses relates to two key factors. First, large magnitude near wellbore tortuosity friction loss increases the pressure required for fracture propagation during pumping. Second, tip extension is a way to dissipate high pumping pressure when very low formation permeability impedes leakoff. Matching transient behavior subject to the presence of both of these factors requires lowering the near-wellbore tortuosity exponent.
Evaluating the Performance of Horizontal Multi-Frac Wells in a Depleted Gas Condensate Reservoir in Sultanate of Oman
Authors: Shaoul Josef R. , Park Jason , Boucher Andrew , Tkachuk Inna , Veeken Cornelis , Salmi Suleiman , Bahri Khalfan , Rashdi Mohammed , Nazaruk Dariusz 
Published: January 2022

Abstract
The Saih Rawl gas condensate field has been producing for 20 years from multiple fractured vertical wells covering a very thick gross interval with varying reservoir permeability. After many years of production, the remaining reserves are mainly in the lowest permeability upper units. A pilot program using horizontal multi-frac wells was started in 2015, and five wells were drilled, stimulated and tested over a four-year period. The number of stages per horizontal well ranged from 6 to 14, but in all cases production was much less than expected based on the number of stages and the production from offset vertical wells producing from the same reservoir units with a single fracture. The scope of this paper is to describe the work that was performed to understand the reason for the lower than expected performance of the horizontal wells, how to improve the performance, and the implementation of those ideas in two additional horizontal wells completed in 2020.
The study workflow was to perform an integrated analysis of fracturing, production and well test data, in order to history match all available data with a consistent reservoir description (permeability and fracture properties). Fracturing data included diagnostic injections (breakdown, step-rate test and minifrac) and main fracture treatments, where net pressure matching was performed. After closure analysis (ACA) was not possible in most cases due to low reservoir pressure and absence of downhole gauges. Post-fracture well test and production matching was performed using 3D reservoir simulation models including local grid refinement to capture fracture dimensions and conductivity.
Based on simulation results, the effective propped fracture half-length seen in the post-frac production was extremely small, on the order of tens of meters, in some of the wells. In other wells, the effective fracture half-length was consistent with the created propped half-length, but the fracture conductivity was extremely small (finite conductivity fracture). The problems with the propped fractures appear to be related to a combination of poor proppant pack cleanup, low proppant concentration and small proppant diameter, compounded by low reservoir pressure which has a negative impact on proppant regained permeability after fracturing with crosslinked gel.
Key conclusions from this study are that 1) using the same fracture design in a horizontal well with transverse fractures will not give the same result as in a vertical well in the same reservoir, 2) the effect of depletion on proppant pack cleanup in high temperature tight gas reservoirs appears to be very strong, requiring an adjustment in fracture design and proppant selection to achieve reasonable fracture conductivity, and 3) achieving sufficient effective propped length and height is key to economic production.
Hydraulic Fracturing as Game Changer to Maximize Waterflooding Efficiency in a Brownfield
Authors: Magna Detto Calcaterra Maria Serena , Sedda Pierluigi , Fulceri Giacomo , Luppina Salvatore , Mauri Luca , Mittiga Vincenzo , Parziale Sabino , Restuccia Gabriele 
Published: January 2022

Abstract
Primary production mechanism of a clean sandstone reservoir in a brownfield for oil production has been recently changed from natural depletion to waterflooding. Despite the apparently moderate petro-physical properties of the formation, injector wells performances were observed to be extremely poor, mainly due to: high drilling-induced formation damage and Fluids interaction within the reservoir (injection across the oil rim section). Several stimulation technologies have been applied to improve wells injection capability for pressure support optimization. Re-perforation via abrasive jetting, perforations wash through coiled tubing and various acid formulations via bullheading were attempted without achieving any significant increase in injectivity. Considering the modest rock permeability, the need to access a wider formation area to improve oil sweep efficiency and the crucial requirement to re-pressurize the reservoir, an additional card was played as last resort: hydraulic fracturing.
This technique was not new to the area and already experimented by different operators. Several producer wells in different layers were hydraulic fracturing stimulated with proppant and/or acid in the past with a good rate of success. Why not to try then?
Given the past experience on the same field with hydraulic fracturing in oil producers and accounting for well integrity and potential injectivity, one was chosen as suitable candidate. Offset wells hystorical data were used to build a hydraulic fracturing reservoir model and plan for the activity in details; operator and service providers engaged in a Frac Well On Paper activity in order to reduce any margin of error during field operations. An approach that proved successful.
From there, the first trial well was planned and performed successfully. 4 other hydraulic fracturing jobs on 4 wells followed at close distance in time with different, but steadily comforting, results. Injection was improved from negligible initial values up to 2000 mc/day for the post-stimulation condition, exceeding the preliminary expectations.
This paper introduces the steps taken to start the hydraulic fracturing campaign, the decision process that led to the design of the treatment, an overview of the execution phases, results well by well and lessons learned to optimize future campaigns.
Prediction Analysis of Induced Casing Deformation of Horizontal Well in Fractured Shale Reservoir: Case Study of Weiyuan Gasfield
Authors: Lu Qianli , Liu Zhuang , Guo Jianchun , Wang Shouyi , He Le , Li Yanchao 
Published: January 2022

Abstract
Casing deformation (CD) is a major challenge for shale gas development in Weiyuan gasfield, natural fracture (NF) slippage is one of the main causes of CD in Weiyuan gas filed. In order to study the mechanism and regularity of NF slippage induced CD, a wellbore shear stress calculation model and a CD degree prediction model are established. And results show that, the approach angle and ground principal stress difference have significant influence on wellbore shear stress, high wellbore shear stress occurs when wellbore orientation is perpendicular to the NF trend. Wellbore shear stress increases with the increase of fracture fluid pressure and NF area, improving casing strength or cementing quality has limited effect on reducing the risk of CD. The smaller the young's modulus, the higher the CD degree, Poisson's ratio has limited effect on CD degree. NF approach and fracture fluid pressure determines the value of CD degree. Field case shows that reasonable fracturing technology to control fracture net pressure and wellbore position arrangement are helpful for reducing CD risk, and the model proposed in this paper can be used to predict CD risk and calculate the CD degree.
When The Last Tree Dies, The Last Man Dies: Do Forests Hold The Key To Survival In Ghana? A Critical Analysis Using The Bootstrapped Rolling Window Granger Causality Test Approach
Authors: Minlah Michael Kaku , Zhang Xibao , Ganyoh Philipine Nelly , Bibi Ayesha 
Published: January 2022

Abstract
This paper investigates the role of forests in the life expectancy of people in Ghana. We test whether the extinction of forests will inevitably lead to extinction of people in Ghana. We first examined the causal relationship between life expectancy and deforestation using the full sample bootstrap Granger causality test approach and find causality to run from deforestation to life expectancy with no feedback from life expectancy to deforestation. Testing for parameter stability, we found the short run and long run parameters of the estimated Vector Auto Regressive models to be unstable. A time-varying approach, the rolling window bootstrapped Granger causality test was then employed to investigate the causal relationship between life expectancy and deforestation. The results showed that deforestation has a negative effect on life expectancy, confirming the widely accepted saying that the health of forests is inextricably linked to the health of mankind. The empirical results further show that, on trend higher life expectancy increases the rate of deforestation in Ghana. Highlighting the importance of the role of forests in influencing life expectancy in Ghana, we recommend awareness creation on the role of forests in supporting human life and also extensive afforestation programs to reduce the rate of deforestation in Ghana. This, we believe, will reduce the spread of vector borne diseases such as malaria and reduce the surge in respiratory diseases which shorten the life span of Ghanaians.JEL codesQ23, Q50, Q53, Q58, Q58