bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimizing Hydraulic Fracturing Design by Analyzing Reservoir, Completion, and Stimulation Parameters and their Influence on Post-Fracturing Gas Rates
Authors: Rahim Zillur , Al-Kanaan Adnan , Kayumov Rifat , Al-Jalal Ziad , Viswanathan Anup 
Published: June 2017

Abstract
With the increase in gas demand and the need to supply additional energy, the focus is now shifted to drilling and production activities exploiting high-pressure/high-temperature (HPHT) tight sandstone gas formations. The design optimization and selection of proper hydraulic fracturing technology is a key to succeeding in getting an economic gas production rate. Using well performance as the primary determining factor, a systematic study and evaluation was conducted on 20 vertical and horizontal wells drilled in HPHT heterogeneous sandstone reservoirs to assess effectiveness of stimulation treatments and benefits of using novel technologies. The numerous variables analyzed to determine the impact on production include different completion options, type of fracturing technology used, various proppant and fluids, fracturing method, production rate, and flowback parameters. A comprehensive database for stimulated wells was created that included reservoir parameters, completion data, minifrac and main stimulation treatment parameters (additives, fluid and proppant types, volumes, rates, and pressures), post-fracturing flowback results, and monthly production data. The production data were normalized on reservoir quality to strengthen the effect of fracturing parameters on well productivity independent of reservoir quality. Correlations were drawn using the Pearson correlation coefficient to compute the upward and downward data trends, ensure use of good quality data, and discard the few nonaligned data. Numerous very useful plots were constructed that show the different trends of the variables evaluated and how they affect production rate.
The results demonstrate the importance of proper well landing with strong influence of reservoir quality on postfracturing production results. The channel fracturing technique offers near-infinite fracture conductivity and shows very promising results compared with conventional treatments. Pumping the bigger fracturing jobs typically yields better production results, but proppant type and schedule should be designed accounting for reservoir quality. Pad volume should be designed to achieve optimum pressure at the end of the treatment, not too high but not too low. Post-fracturing production parameters are as important for the well performance as the stimulation treatment itself. The analyses identified the key post-fracturing production drivers in the gas reservoirs and ways to improve production of future wells drilled in various formations under similar conditions.
Validating Hydraulic Fracturing Properties in Reservoir Simulation Using Artificial Neural Networks
Authors: BuKhamseen Nader Y. , Ertekin Turgay 
Published: June 2017

Abstract
This paper presents a workflow to validate the hydraulic fracture properties in the reservoir simulator after the fracture job has been completed. The workflow incorporates artificial neural networks (ANN) as the engine behind the validation process. The required hydraulic fracture parameters that need to be fed to the reservoir simulator are mainly the fracture half-length, fracture permeability, and fracture width. These parameters constitute the fracture conductivity and are used to match the production and pressure profiles after the fracture job is completed.
If the reservoir simulation model has a satisfactory history match, the model response after the fracture job should not drastically deviate from the observed well response. If that deviation occurs, the developed ANN is introduced to help in figuring out a set of fracture conductivity parameters that match the observed data. The process starts by running the reservoir simulator to generate several data sets with variable fracture conductivity parameters to be used for training and testing the ANN. The ANN then outputs the fracture conductivity parameters based on the observed pressure and production profiles. The suggested output of the ANN is eventually validated with the reservoir simulator to check for the results accuracy.
This workflow has been theoretically tested on a synthetic reservoir model with heterogeneous reservoir properties. A fracking job of up to five stages is performed on wells in a low permeability oil reservoir. Results show the ANN is able to reproduce the fracture conductivity parameters with up to 84% accuracy when the stimulated well has been in production for one year. This number rises to 96% when additional year of production data is collected.
The availability of different training algorithms makes the artificial neural networks a fast and reliable tool to analyze the relationships between various parameters. As the results of this paper suggest, the reservoir simulation model can be updated with the aid of ANN and without compromising the captured physics during the history match.
Two Component Lost Circulation Material for Controlling Seepage to Moderate Losses
Authors: Ramasamy Jothibasu , Amanullah Md 
Published: June 2017

Abstract
A two-component lost circulation material (LCM) system is developed to mitigate seepage to moderate type loss of circulation using materials and polymers having different physical and chemical properties. The first component or component I is a slurry containing a carrier fluid such as water, a particulate or filler material such as fly ash, a fibrous material such as polypropylene fibers, and a water absorbing acrylic polymer. The second component or component II is a solution of sodium hydroxide in water. Component II is used as activator and when in contact with component I, the sodium hydroxide triggers the polyacrylic polymers in component I to absorb water in the slurry. As a result the whole system is swollen up and a generation of thick mass of the system achieved. This approach is used to address the lost circulation scenarios while drilling through fractured and cavernous zones. A comprehensive lab testing of the two component lost circulation material system has been carried out using pore plugging test (PPT) apparatus to prove its efficiency to seal off the fractures of width up to 2 mm. The results of PPT experiments show that the two component lost circulation material system is capable of controlling loss of circulation into fractures of width up to 2 mm under high pressure (1500 psi) and high temperature (250 °F) conditions. The new two component lost circulation system will provide a reliable solution to address seepage to moderate type loss of circulation.
Pressure Transient Analysis of Vertically Fractured Well in Tight Oil Reservoirs with Rectangle Stimulated Reservoir Volume
Authors: Zhu Langtao , Liao Xinwei , Chen Zhiming 
Published: June 2017

Abstract
The technique of stimulated reservoir volume (SRV) is becoming a key measure to enhance vertical well productivity and ultimate recovery in tight oil reservoirs. After the SRV treatment, micro-seismic monitoring strongly shows approximate rectangle stimulated reservoir volumes with a single bi-wing fracture are generated. However, most published works on the pressure transient of vertically fractured wells assumed that the SRV is an approximate circle, and few works have been done to rectangle SRV.
In this paper, a new analytical pressure transient solution for vertically fractured wells (VFW), with rectangle SRV and a single bi-wing fracture, is derived under constant rate. First, a two-region composite model is established to model the VFW. The inner region is considered as rectangle dual-porosity with a single bi-wing fracture. In addition, this model also considers other multiple factors including stress-sensitivity effect of permeability, unsteady cross flow between matrix and fractures. Then, the trilinear flow model proposed by Brown is extended to handle the rectangle boundary and bi-wing fracture; the Pedrosa's perturbation and Laplace transformation are applied to solve the non-linear equation, and the Kazemi's method is adopted to simulate the unsteady cross flow, and the pressure equation for VFW is solved. After that, this analytical solution is applied to the real cases from Ordos Basin reservoir to conduct equation validation. Finally, sensitivity studies are conducted to evaluate the effect of some critical parameters on pressure behavior of VFW.
The results of verification show there are great agreements. Results from this study show that the special flow regimes for a VFW in tight oil reservoirs includes (1) linear flow for the effect of bi-wing fracture conductivity, (2) SRV width effect flow, (3) inner boundary-dominated flow. The linear flow is stronger with the increase of bi-wing fracture length, bi-wing fracture conductivity, and SRV width. As the permeability of SRV increases, the inner boundary-dominated flow becomes more obvious. In addition, the SRV linear flow is stronger with the increase of SRV volume.
This work provides significant references for reservoir engineers in pressure transient analysis as well as fracturing evaluations of vertically fractured wells in the tight oil reservoirs.
Effect of Gravity on Near-Miscible CO2 Flooding
Authors: Al-Riyami Hamed F. , Kamali Fatemeh , Hussain Furqan 
Published: June 2017

Abstract
Carbon Dioxide (CO2) injection is considered one of the most widely used enhanced oil recovery (EOR) methods due to CO2 availability, applicability. Contributing to its popularity is the ability to perform carbon capturing and storage alongside EOR in which CO2 is stored in reservoirs to mitigate global warming potential. Experiments have been performed to measure oil recovery factor, CO2 storage efficiency, and co-optimization function of a CO2 flood in horizontal cores but none has studied the effect of gravity on all three.
This paper presents horizontal and vertical CO2 flooding experiments to quantify the gravity effect on oil recovery and CO2 storage. Irreducible water saturation of 27% represents the initial condition for both experiments. A homogeneous Bentheimer sandstone core is used while a mixture of hexane (65%) and decane (35%) represents the oil phase. The Oil recovery, pressure drop and effluent compositions are recorded during the experiment.
It was found that vertical flood exhibited high displacement efficiency but low volumetric sweep efficiency and by eliminating the effect of gravity, not only oil recovery increases, but also CO2 storage efficiency. In the vertical flood, oil recovery, CO2 storage efficiency, and the co-optimization function increase by 24%, 7%, and 15%, respectively, compared to horizontal flood. The stabilized displacement front delays breakthrough and effectively improves oil recovery and storage efficiency.
Nano-Scale Imaging at Crude Oil/Brine/Rock Interface in Carbonates: A Pore Scale Approach
Authors: Gmira A. , Al-Enezi S. M. , Cha D. K. , Yousef A. A. 
Published: June 2017

Abstract
Smart water and low-salinity waterflooding showed encouraging results for oil recovery in carbonate and sandstone reservoirs. Therefore, understanding of multiphase flow phenomena in reservoir rocks is critical to optimize injected water formulations and increase oil recovery. Various micro- and macroscopic techniques including NMR, surface charges, IFT, contact angle and coreflooding have been extensively used to understand the underlying mechanisms responsible for rock wettability alteration. However, it is challenging to understand the behavior of reservoir fluids and carbonate rocks at nano-scale with conventional methods, hence there is a need for advanced technologies to identify fluid phases and distributions at pore scale. The primary objective of this study is to develop an experimental protocol using Cryogenic high resolution focused ion beam (Cryo-FIB SEM) equipped with energy dispersive spectroscopy (EDS) and apply the developed protocol to study the impact of ions on carbonate rock/crude oil/brine interface at nano-scale. Cryo FIB-SEM preparation and imaging provide pore structure, connectivity and fluids distribution at carbonate pore scale. While, EDX analysis gives an insight of the compositional distribution and elements mapping. For carbonates exposed to calcium chlorides, SEM analysis showed the presence of hydrocarbons with a newly formed phase inside the pores, indicating the presence of high concentration of oxygen bonds. While no newly formed phase was observed for carbonate rock exposed to a complex brine. EDS analysis have also provided an elemental mapping based on the composition of the brine used. This feasibility study showed that the experimental protocol permits the observation of carbonate porosity morphology, fluids distributions inside the pore and elemental mapping across the surface for a better understanding of the crude oil/brine/carbonate system.
Use of Local Binary Pattern in Texture Classification of Carbonate Rock Micro-CT Images
Authors: Rahimov Khurshed , AlSumaiti Ali M. , AlMarzouqi Hasan , Jouini Mohamed Soufiane 
Published: June 2017

Abstract
A newly emerged technique known as Digital Rock Physics demonstrates an ability to characterize properties of the porous media. This technique is based on the imaging of rock micro-structure using a micro-CT scanner. Images are segmented based on their grayscale values to extract pore network from the solid phase. Then, rock properties are estimated using extracted pore network and numerical simulations. Porosity and absolute permeability are two essential properties that can be derived from grayscale images. These properties represent storage and flow capacity of the rock.
Some rock samples, particularly carbonate rocks have complex micro-structures at several length scales. Due to limited image resolution, 3D images of carbonate rock may not have top-bottom pore connectivity. In this case, one unable to simulate fluid flow throughout the images. Therefore, permeability is computed on small image sub-volumes, where pore connectivity is revealed locally. Such approach requires long simulation runs.
In this paper, a new approach is proposed to estimate permeability from 3D carbonate rock images, where pore connectivity is not revealed from top to bottom. In this approach, first a number of texture classes that represents various textures in the 3D image are identified. For each identified texture class, several sub-volumes from the 3D image are extracted. These sub-volumes are representative of the identified textures and have local pore connectivity. To simulate fluid flow through the pore network of extracted sub-volumes Lattice Boltzmann method (LBM) is used. Permeability is then calculated using Darcy's equation. After determining permeability ranges of each textural class, the 3D image is divided into sub-volumes. Then, each sub-volume is classified into one of the specified texture classes using a modified version of the texture classification algorithm, Local Binary Pattern (LBP). In this study, traditional 2D LBP texture feature vector is adopted to handle 3D volume classification. After classification, each sub-volume is assigned a permeability value that is equivalent to its texture class. Finally, the permeability of the whole 3D image is computed by simulating Darcy's flow through the all sub-volumes.
Preliminary outcomes of the proposed technique indicate that it is able to closely estimate experimental results from the laboratory.
Remaining Oil Saturation Measurements for CO2-EOR Pilot in Saudi Arabia
Authors: AlOtaibi Fawaz , AlOsaimi Falah , Sanni Modiu , Kokal Sunil , Ali Razally , Alhashboul Almohanand 
Published: June 2017

Abstract
Enhanced oil recovery by CO2 injection is an effective method for recovering additional oil beyond water flooding. In recent years CO2-EOR has garnered considerable attention from an environmental perspective as it is considered a green-house gas. Saudi Aramco is implementing its first CO2-EOR and sequestration pilot project in a slightly depleted part of a carbonate reservoir. An important aspect of the pilot testing is the measurements of remaining oil saturation (ROS) before and after the CO2 flooding. This paper discusses a number of methods and techniques for ROS quantification before CO2 injection in the ongoing CO2-EOR pilot project. The suite of tests provide pre-CO2 injection saturations. Similar tests are planned post-CO2 injection to determine the reduction in ROS after the pilot has been completed.
Several methods have previously been used to determine ROS in oil reservoirs. In this study different logging technologies were utilized for quantification of ROS before CO2 injection to generate baseline data. The logging included resistivity and dielectric techniques. These techniques were also combined with physical formation fluid tester and sponge core analysis to determine ROS in the targeted carbonate reservoir. Finally the results are compared with a single well chemical tracer test which was conducted in the area.
This paper presents the results from various methods and explores the effect of different parameters such as lithology, porosity, salinity and water saturation on ROS quantification. The results from near wellbore techniques are compared with data from sponge core as well as the single well chemical tracer test. Methodologies of raw data processing and their interrelations are shared. This paper provides new insights into how various logging tools and coring can be optimized in the future to increase the certainty of ROS measurements.
Hemp Yields and Its Rotation Effects on Wheat under Rainfed Mediterranean Conditions
Authors: Gorchs Gil , Lloveras Jaume , Serrano Lydia , Cela Sebastián 
Published: June 2017

Core Ideas
Rainfed Mediterranean environments might be suitable for double‐purpose hemp production.
Hemp is a good predecessor for wheat under rainfed Mediterranean conditions.
The beneficial effects of hemp on the subsequent wheat yield appear to last for 2 yr.
Monocropping hemp over 2 yr, does not reduce its grain and biomass yields.
Hemp (Cannabis sativa L.) has a low impact on the environment requiring few added resources, and has multiple downstream applications. There is little information on hemp biomass, seed yields, and response to NPK fertilization under humid rainfed Mediterranean conditions. Moreover, the effects of hemp on subsequent wheat (Triticum aestivum L.) crops have not been determined. To address these issues, we performed a field study for 6 yr in Catalonia (northeastern Spain). Hemp treatments included: hemp monoculture, unfertilized hemp succeeding wheat, and NPK‐fertilized hemp succeeding wheat. In turn, wheat treatments included: wheat monoculture, first‐, second‐, and third‐year wheat succeeding unfertilized hemp, and first‐, second‐, and third‐year wheat succeeding NPK‐fertilized hemp. The hemp biomass yields (5340–10,090 kg ha−1) were similar to or lower than those achieved in other European regions whereas the hemp seed yields were relatively high (604–1434 kg ha−1). Both the biomass yield and seed yield greatly increased with NPK fertilization. The rotation effects of hemp on the subsequent wheat crops increased the wheat yield by 1368 and 155 kg ha−1 in the first and second years, respectively, but in the third year the yield was similar to the wheat monoculture. The beneficial effects of hemp on wheat therefore appear to last for 2 yr. We conclude that dual‐purpose hemp (harvested for fiber and seed) is an excellent predecessor for wheat, improving the sustainability of cereal‐based cropping systems under humid rainfed Mediterranean conditions.
Can Edaphic Variables Improve DTPA‐Based Zinc Diagnosis in Corn?
Authors: Barbieri Pablo A. , Sainz Rozas Hernán R. , Wyngaard Nicolás , Eyherabide Mercedes , Reussi Calvo Nahuel I. , Salvagiotti Fernando , Correndo Adrián A. , Barbagelata Pedro A. , Espósito Goya Gabriel P. , Colazo Juan C. , Echeverría Hernán E. 
Published: June 2017

Core Ideas
DTPA‐extractable Zn is often used to predict corn response to Zn application.
Can DTPA–Zn‐based diagnosis be improved by considering other soil properties?
Soil properties did not contribute to explain corn grain yield response.
DTPA–Zn allowed to discriminate sites based on their response to Zn fertilization.
We determined a Zn‐critical range from 0.86 to 1.30 mg kg−1 (n = 64).
Current zinc (Zn) diagnostic methods for corn (Zea mays L.) are often based on soil DTPA (diethylenetriamine‐pentaacetic acid) extractable Zn (DTPA‐Zn). However, calibration of the DTPA‐Zn test may be influenced by other soil properties such as pH, organic matter (SOM) and available Bray‐P (PBray‐1). Our objective was to assess the contribution of soil properties to a DTPA‐Zn model used to predict corn response to Zn fertilization. We conducted 64 field trials with two Zn‐fertilization treatments: with and without Zn fertilization. In all sites, we measured SOM, PBray‐1, pH, and DTPA‐Zn at 0‐ to 20‐cm depth before sowing. Yield difference between Zn‐fertilized and unfertilized treatments (Ydifference) was significant in 33% of the experimental site‐years. In responsive site‐years, the average Ydifference was 0.98 Mg ha‐1 (11.4%). Soil organic matter was the only property that was a significant addition to the DTPA‐Zn model for predicting the corn relative yield (Model R2 including SOM = 0.27). However, the improvement was nominal (Partial R2 of SOM = 0.06). Use of DTPA‐Zn alone was suitable to discriminate Zn responsiveness among site‐years based on the Ydifference by correctly diagnosing 81% of the outcomes. We determined three soil DPTA‐Zn ranges with different probability of resulting in a Ydifference greater than zero when fertilized with Zn: high (<0.9 mg kg‐1), medium (0.9–1.3 mg kg‐1), and low (>1.3 mg kg‐1). These soil‐test‐based Zn recommendations improve the identification of Zn‐deficient soils allowing prevention of yield loss from Zn deficiency and more rational use of Zn fertilizers.