bluuebunny/crossref_metadata_2025_split huggingface dataset:
Far-Field Diversion System Designed for Slickwater Fracturing
Authors: Vigderman Leonid , Bogdan Andrey , Shen Lingjuan , Heller David , Yeung Tony , Fu Diankui 
Published: October 2018

Abstract
Fracture geometry control and increased fracture complexity have been recognized to be critical factors in optimizing unconventional well completion design as well as preventing detrimental frac hits. A major challenge of far-field diversion in slickwater fracturing is ensuring transport of material to the fracture tip or secondary fracture in a low-viscosity fluid. This paper will present a novel far-field diverter system for fracturing with low-viscosity fluids to address these challenges composed of an engineered mixture of unique ultra-lightweight proppant and degradable material. Not only can the system effectively divert fracturing to control fracture geometry and enforce complexity, but will also maintain fracture conductivity.
Several types of tests were performed to determine the effectiveness and optimize the design of the far-field diverter system. First, a series of slot plugging tests were carried out to optimize diversion performance of the system by blocking fluid flow through targeted fracture widths while maintaining flow through the larger portions of a fracture. Next, the diverter was pumped through a flow apparatus to demonstrate its far-field transportability in low-viscosity fluids. Finally, conductivity of the diverter system after degradation was tested.
The new far-field diverter system was designed to create a permeability barrier at the fracture tip to contain fracture length growth as well as to be used in the middle of a stage to control growth of secondary/tertiary fractures to allow redistribution of fracturing fluid within the rock to further increase complexity. Lab tests demonstrated that by controlling the particle size of the engineered proppant and diverter mixture, the diverter system can be tailored to plug different fracture widths. Significantly, flow tests using a low-viscosity, slickwater fluid demonstrated the excellent transport properties and limited settling rate of the diverter. Finally, conductivity tests showed that by using an engineered mixture of non-degradable, ultra-lightweight proppant and degradable material, conductivity in the fracture is maintained after particle degradation, which is critical when applied in the middle of a stage to increase fracture complexity.
To the authors’ knowledge, this is the first published paper of a far-field diverter that is optimized for slickwater fracturing for both fracture geometry and complexity control. The new diverter technology overcomes the significant limitations of other available systems such as fracture closure, inadequate transport to the far field, or the requirement to use high viscosity fluids.
Improved Efficiency of a Nitrate Reducing Bacteria/Nitrate Treatment by the Incorporation of a Sulfate Analog
Authors: Gawas Kiran , Safarin Dana , Riley Howard , Ogle James 
Published: October 2018

Abstract
Hydraulic fracturing in the Marcellus Shale play has moved to produced water only scenarios because of prohibitive water disposal costs. Well completion under produced water only conditions increases the demand on chemical additive performance. In addition, water reuse selects deleterious microorganisms through natural selection, which may increase the likelihood of formation souring. Conventional biocides are typically used to mitigate these risks, but to some extent, they present health, safety, and environmental (HSE) concerns. In addition, several conventional biocides have side reactions with sulfide, notably tetrakis(hydroxymethyl)phosphonium sulfate (THPS) and 2,2-dibromo-3-nitrilopropionamide (DBNPA). This paper describes an improved method for the effective control of deleterious microorganisms without the use of conventional biocides.
An environmentally friendly system that includes nitrate-reducing bacteria (NRB) coupled with nitrate co-introduction was previously shown to mitigate souring as effectively as a biocide alternative for more than 1,000 assets. The NRB inhibit growth of the deleterious sulfate-reducing bacteria (SRB) primarily by competing for the available carbon source if the source is limited. This paper describes an improved NRB/nitrate system that incorporates a sulfate analog, which presumably inhibits dissimilatory sulfate reduction and enhances mitigation. Laboratory experiments were performed to measure the amount of hydrogen sulfide (H2S) produced in field brine samples inoculated with SRB. The improved NRB/nitrate system was shown to inhibit the production of H2S under worst-case scenarios in laboratory competitive exclusion experiments.
Results for the new treatment at four trial wells are presented. Sulfate-reducing bacteria populations, acid-reducing bacteria populations, and a gaseous H2S concentration were monitored over three months and were found to satisfy the operator's set key performance indicators. Overall, the amount of chemical required for treatment was reduced for this improved system, which substantially reduced the operator costs to treat the wells.
The combination of chemistries with mutually exclusive cellular targets highlights the value of synergistic effects, specifically reducing system cost to treat while retaining low aquatic toxicity, as compared to traditional biocides used in the oilfield.
Understanding Development Drivers in Horizontal Wellbores in the Midland Basin
Authors: Cherian Bilu , Shoemaker Michael , Nwoko Stephanie , Narasimhan Santhosh , Olaoye Olubiyi , Iqbal Javed , Peacock Joshua , Becher John , Ferguson Brittney , Zakhour Nancy 
Published: October 2018

AbstractThe Permian Basin in North American has been the driving force behind global energy growth, resulting from the exploitation of unconventional resources. The combination of high quality stacked resources, horizontal drilling, completion tools, and hydraulic fracturing innovations has accelerated the learning curve in this basin over the past few years: which was the impetus of this study.This paper utilizes an integrated model approach to understand reservoir performance on a pad with four wells completed across multiple horizons in the Midland Basin. Rich multi-domain data sets were utilized that included seismic, wireline triple-combo, compressional and shear log suites, core (rock mechanics testing, geochemical analysis (XRF and XRD) and routine core analysis), completion data (fracture treatments with pre-and post-job shut-in pressures), and production data including 1,500 days of production history with bottom-hole pressure gauge data. 3-D surface seismic, high tier logs, and core data were used initially to create a facies model. Properties were distributed into a geo-model using the existing vertical well-control and seismic as constraints. A sector model was then built that enabled modeling of 4 development wells that consisted of parent well, followed by 3 child-wells. The history matching of fracture treatments and production data with bottom-hole pressure data resulted in significant understanding of key parameters driving subsurface performance.A workflow, representing the seamless integration of said models, is presented that enables an improved understanding of what impact sequence and timing of operations has on the subsurface contact area as well as the implied change in well performance if an optimal strategy is executed. Geomechanical facies that drive vertical connectivity and fracture geometry, as well as reservoir parameters that impact fracture contact with the reservoir, were identified.
Drilling Extended Laterals in the Marcellus Shale
Authors: Doak Joshua , Kravits Matthew , Spartz Michael , Quinn Pat 
Published: October 2018

Abstract
A drilling team has focused on increasing lateral lengths in the Marcellus Shale over the past couple of years. The team reevaluated prior drilling processes that had been in place for 7,000’ to 9,000’ laterals in order to determine what operational practices would need to be revised in order to drill and case laterals in excess of 18,000’. We focused on rig upgrades, directional tools, drilling fluids, casing floatation and other best practices. We even implemented field trials on various lateral lengths in efforts to evaluate extended lateral practices prior to drilling the first 18,000’ lateral.
Over the twelve month period of revised processes and upgrades, we drilled thirty-four horizontal wells each exceeding 12,000’ in lateral length – this included two wells in excess of 17,850’ with one exceeding 18,000', which represented the first drilled Marcellus lateral to exceed that length. This paper covers the details of those processes and upgrades that led to dozens of successful Marcellus horizontal wells with extended lateral lengths.
Impacts of Field Depletion on Future Infill Drilling Plans in the Marcellus Shale
Authors: Shahkarami Alireza , Wang Guochang , Rohland Zachary 
Published: October 2018

Abstract
The development of shale assets has reached a point where operators face the challenge of infill drilling. The scope of this project is to investigate the impact of neighboring well pads on the performance of a newly developed well/pad. This paper highlights the differences in production performance of "old" pads versus "new" well and analyzes how the depletion history of the existing pads affects the performance of new well.
The study area covers two pads: Pad A and Pad B which have 10 and 12 wells respectively; these wells have been producing since 2016 from the dry gas region of Marcellus Shale in southwestern Pennsylvania. Pad A and Pad B are more than 9000 ft apart, and the region between these two pads has potential for future development. For this project, a 3-D reservoir simulation model that includes both pads was built and calibrated to match past performance of Pad A and Pad B. The calibrated simulation model then was utilized for developing new wells. The reservoir simulation model was used to perform a sensitivity analysis on reservoir characteristics and the impact of Pad A and Pad B's depletion history on the performance of new well(s). The workflow involves optimizing the well spacing of proposed well(s) with/without considering the depletion history.
Usually, with the very low permeability of shale reservoirs, the depletion history of neighboring wells is expected to affect the performance of newly developed wells. The new wells are considered as a different well pad, and their stimulated reservoir volume does not overlap with the Pad A and Pad B. However, the region average reservoir pressure is reduced due to the Pad A and Pad B production history. In most of shale reservoir numeral simulation studies, the reservoir is considered virgin. The average reservoir pressure potentially impacts the well spacing optimization workflow as well as the designing of an effective well completion job. In this study we compare two scenarios. One scenario considers the depletion history of neighboring well pads and the other one does not. The net present value optimization was done with and without considering the impact of depletion history.
This project studies the effects of neighboring well pads on production performance of newly developed pad. Compared to the interaction of parent/child well in a single well pad, multi-pad studies are rare primarily because of the high computational cost associated with a multi-pad numerical simulation analysis.
An Integrated Approach to Optimize Perforation Cluster Parameters for Horizontal Wells in Tight Oil Reservoirs
Authors: Lu Yu , Li Haitao , Lu Cong , Liu Chang , Chen Zhangxin 
Published: October 2018

Abstract
Perforation parameters have a great influence on the performance of the multi-stage fracturing horizontal wells in tight oil reservoirs. Optimizing perforation cluster parameters is able to solve many detrimental issues, including many null perforation clusters without the produced oil, the unevenly distributed output in each stage along horizontal wells, and no complex fracture network always created near the fractured wellbore. To achieve the better performance of the volume fracturing, a practical integrated approach is proposed to optimize perforation cluster parameters. First, based on the good logging data, we establish an evaluation method for the fracability and reservoir properties to select the perforation interval. Second, a mathematical model based on the stress shadow and hydraulic fracture propagation are proposed to optimize the cluster spacing and cluster parameters within each cluster in the same stage, and the un-uniform cluster spacing and perforation number in each cluster are studied. Finally, a case well is successfully conducted with the proposed approach in the tight oil reservoir. Results show that i) the lateral with higher fracability index and property index can be treated as perforation intervals; ii) the un-uniform perforation cluster spacing and the uneven perforation number can obtain a more uniform fracture propagation morphology. The approach can better prevent the generation of ineffective perforation clusters and obtain more complex fracture networks and a better SRV. This also guides to design completion strategy and improves the economic benefits.
A Systematic Approach for Reducing Scaling Effects and Enhancing Production in Depleted Carbonate Reservoirs in the Permian Basin
Authors: Boulis Tasos , Millsaps Logan , Troutman Tony , Polk Dustin 
Published: October 2018

Abstract
Scaling precipitation in the form of calcium or iron sulfate (CaSO4 – FeSO4) appears to be a common problem in most of the wells completed in the Yeso formation in the Permian Basin. Accumulation of these forms of scale in the perforations and the downhole equipment can create severe production losses and therefore they require constant, some times costly, treatments. Additionally, their presence in the wellbore hinders the efficiency of the acidizing procedures, performed by the operators to further increase the productivity of their wells.
The objective of this paper is to present an innovative workflow, which significantly reduces the scaling effects and allows the acidizing of these carbonate reservoirs to be more efficient. Results are avialble for more than 20 wells, from Occidental Petroleum’s assets in the North New Mexico region. Details regarding the evolution of the procedure, the types and amounts of the chemicals are extensively discussed in this paper.
The procedure starts with the candidate well selection, which preferably are located in the highest OOIP areas to maximize the efficiency. The second step involves the water sampling and analysis to determine the types of scaling and consequently the required chemical treatment. The innovation in this step has to do with the time that converters are left in the wellbore and the extra chemicals that have been added compared to the previous procedures. The last step involves the deployment of the acid downhole, where three different methodologies have been tested and evaluated based on their efficiency and well returns.
The proposed approach has been successfully applied to more than 20 wells and the results are encouraging showing an average incremental oil production of ~600% while the execution cost remains very low.
Optimized Rock Fluid Interaction and Stimulation Intensity Enhancement Improves Well Performance: A Marcellus Case Study
Authors: Budney Tim , Jose Chirinos , Jacot Henry , Svarczkopf Tim 
Published: October 2018

Abstract
Large volume slick-water stimulations have become the de facto standard for completion strategy in the Upper Devonian, Marcellus, and Utica/Point Pleasant. Current completion optimization work has focused on optimizing stage spacing, sand loading, and injection rate which have shown increases in well productivity. One commonly overlooked variable in the design equation is stimulation fluid chemistry and rock/fluid interaction. Friction reducers, the primary additive of a slickwater system, have become a commodity with many service companies providing similar systems. Premium slickwater systems in the Marcellus are generally characterized by the ability to tolerate high percentages of produced water.
We have developed an alternative approach to the design of stimulation fluid chemistry. This approach consists of creating a comprehensive laboratory workflow justification for multiple fluid combinations with consideration for specific thermal maturity windows. The laboratory workflow includes proprietary rock/ fluid interaction tests that insure formation compatibility, lever imbibition/displacement production mechanisms, insure compatibility of fluid components inclusive of available water sources, and insure optimization of the fluid based on stimulation intensity (Budney 2017) objectives. After extensive testing, a new stimulation fluid chemistry has been developed that offers several advantages verified by laboratory testing. The new stimulation fluid chemistry consists of a multifunctional additive with the following characteristics: salt tolerant, viscosifying, formation stabilizing, wettability enhancing friction reducer technology paired with a compatible scale inhibitor and biocide. This new stimulation fluid chemistry was field tested against an incumbent fluid chemistry provided by the stimulation service company. Well production data from the first multiple well experiment demonstrated the new stimulation fluid chemistry resulted in significantly improved well performance. A second multi-well experiment in a different area was conducted and proved the well performance improvement associated with the new stimulation fluid chemistry was repeatable. Economic analyses on wells from both field experiments demonstrate an excellent return on investment with the new stimulation fluid chemistry.
This study highlights the importance of justifying stimulation fluid chemistry utilizing a laboratory workflow. The laboratory workflow incorporates rock/fluid interaction testing to maximize the imbibition/displacement production mechanism. The laboratory workflow must also prove that the stimulation fluid chemistry satisfies the stimulation intensity objectives of high rate, high sand concentration, and reduced fluid volumes while enabling reliable field execution.
A Semi-Analytical Model for Computation of Maximum Sand Free Production Rate in a Perforated Horizontal Well
Authors: Wu Zhan , Suryanarayana P. V. , Vasantharajan Sriram 
Published: October 2018

Abstract
A semi-analytical framework for predicting the onset of sand production in a horizontal well is presented. The approach couples the flow in perforation tunnels with flow in the wellbore itself, to obtain a more accurate estimate of maximum sand free production rate in a well. The elastic equations of equilibrium are combined with the Mohr–Coulomb failure criterion to calculate the critical radius. A numerical, iterative solution method is used to compute the location of the elastic-plastic zone during well production. Instead of computing the pressure change in a cavity, which is difficult to characterize and implement in practice, the proposed model integrates the cavity stability criteria into the perforated wellbore inflow model to determine maximum sand-free wellbore flow rate. In addition to the typical perforation tunnel parameters such as cohesive strength, friction angle and perforation radius considered in past efforts, pressure loss effects in a wellbore (wall friction, acceleration, and fluid mixing) are incorporated into the proposed model. A numerical shooting method is then used to iteratively arrive at the maximum sand free rate for a perforated horizontal wellbore in a reservoir of known properties. Results show that without incorporation of the inflow model, the predicted maximum sand-free rates from prevailing approaches can be over-optimistic. The proposed method can be used to optimize perforation parameters to prevent sanding when designing well completions.
Study of Cluster Efficiency in Unconventional Reservoirs by Analytical Simulators
Authors: Ibrahim Mohamed Mohamed , Coskuner Yakup , Salah Mohamed Mohamed , Ibrahim Mazher , Mahmoud Omar , Pieprzica Chester 
Published: October 2018

Abstract
Unconventional reservoirs have been defined as formations that cannot be produced at economic flow rates or that do not produce economic volumes of oil and gas without horizontal well with hydraulic fracture treatments. Horizontal well fracturing efficiency in unconventional reservoirs is the main factor for the success of developing unconventional reservoirs. The early focus of the industry was on the operational efficiency and during this period, the geometric spacing of perforation clusters adopted as the preferred completion method. Cipolla et al. (2011) presented a case study on the interpretation of production logs from hundreds of horizontal wells. The results indicated that 60% of perforation clusters contribute to production when completed geometrically and completion cost could reach more than 60% of the total well cost. Recently, numerous studies have been undertaken to understand this phenomenon. Increasing the stimulation effectiveness and maximizing the number of perforation clusters contributing to productivity was an obvious area for improvement to engineer the completion design.
The uniform initiation and distribution of fractures in each frac stage is very complex because there are many factors affecting the fracture initiation such as stress orientation, heterogeneity, existing of natural fractures, and completion design. This paper presents sensitivity studies investigating the effect of the formation permeability, fracture spacing, fracture half-length, fracture conductivity, flowing bottom hole pressure, and outer reservoir permeability on the well ultimate recovery efficiency by using analytical simulator.
Characterization of the CO2-Fluid-Shale Interface Via Feature Relocation Using Field-Emission Scanning Electron Microscopy, in Situ Infrared Spectroscopy, and Pore Size Analysis
Authors: Goodman Angela , Sanguinito Sean , Kutchko Barbara , Natesakhawat Sittichai , Culp Jeff 
Published: October 2018

Abstract
Fundamental research targeting the interactions of CO2 and fluids with unconventional shale systems is limited from the perspective of using carbon dioxide 1) as an alternative fracturing fluid, 2) as an agent to enhance hydrocarbon production, and 3) as an injection agent into the shale formation for storage purposes to avert emissions to the atmosphere. In this work, we apply in-situ infrared spectroscopy (FT-IR), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), and Brunauer-Emmett-Teller (BET) surface area and density functional theory (DFT) pore size analysis to examine the effects of CO2 and fluid on the Marcellus and Utica Shales. Results show changes to the shale at both the micron and nanometer scale after reaction with CO2 and water. These alterations could potentially alter overall permeability and fracture networks that may cause issues for future EOR activities, CO2 storage, and/or the practice of using CO2 as a hydraulic fracturing material.