bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improving Land Transport Contractor Driving Safety Performance
Authors: Condor Juan Carlos , Villarreal Gonzalo 
Published: June 2014

Abstract
Driving is identified as the work-related activity with one of the highest risks in the oil and gas industry, and in many countries the annual numbers of driving-related incidents have been rising in recent years. A study conducted by the World Health Organization (WHO) predicts that road-related fatalities will continue to increase, and will become an even higher contributor to global mortality. According to safety performance indicator reports produced by the Oil & Gas Producers Association (OGP), land transport is one of the activities with the highest number of fatalities, and most of these fatalities involved land transport contractors (LTCs). Similar root causes were identified in most of these fatal incidents, and these included not following procedures, poor driving behaviors, and inadequate or defective vehicle safety features.
In 2010, an oilfield services company put in place new guidelines aimed at increasing the levels of HSE compliance among all of its LTCs. The guidelines were designed based on prior experience of LTC weaknesses related to HSE management and risk exposure while en-route. The guidelines defined specific requirements to enhance HSE management and improve LTC HSE performance through compliance with the requirements, such as effective training and vehicle safety features.
This paper describes some of the outcomes of the new guidelines when implemented in Colombia and Peru. These include a new LTC contracting process implemented with the participation of all relevant company departments. Specific processes have been introduced to measure the level of compliance with contractual HSE requirements and performance assessment tools. The authors discuss how results of the guidelines include improving HSE culture among the company’s LTCs, who are more motivated to implement effective HSE management systems over the long term. The company’s automotive incident rate has in Colombia and Peru has improved by more than 20% over the last two years. There has also been an increase in monthly LTC contracts and an associated reduction in the utilization of LTC’s on a call-out basis, which has historically represented the service with the highest risk.
Improvements in Multistage Fracturing, Remolino Field, Mexico
Authors: Gutierrez G. , Ramirez L. , Sierra J. R. , Medina E. , Gutierrez L. J. , Salguero J. 
Published: June 2014

Abstract
During the past few years, the oil industry in Mexico has taken significant steps toward improving the economic performance of hydrocarbon-producing wells in the very low-permeability, heterogeneous, compartmentalized, and hard-to-produce reservoirs of the Chicontepec paleochannel through the application of high-impact technologies used in unconventional wells for drilling, logging, perforating, zonal isolation, completions, fracturing, etc. that unquestionably helped improve well performance. However, the proper integration of these new technologies in the heavy-oil Remolino field, located in southern Chicontepec, has shown the potential to deliver better results in terms of production and recovery improvement.
Some of the production problems of Remolino field include previous ineffective stimulations, low reservoir contact area, poor well productivity, and extremely low recovery factors. These problems were addressed by modifying (i) the well architecture from vertical to horizontal, (ii) the zonal isolation from conventional cemented to engineered cemented and swell-packer openhole, (iii) the wellbore-reservoir connection from perforating to hydrajetting and ball-activated sleeves, (iv) the fracturing fluids from conventional crosslinked to hybrid fluids, and (v) the fracture design and pumping schedule to achieve the required length and conductivity. The application of these completion technologies in Remolino field have evolved, based on production results and operational efficiency, from the simplest perf-and-plug method in vertical wells to more complex coiled-tubing assisted fracturing and faster ball-activated sleeves in horizontal wells. Lowering the completion time also has been a primary driving factor for choosing the proper completion option for each individual well, attempting to achieve faster fracturing and quicker production.
The experience of applying new technologies in Remolino field is presented in this paper, including comparisons between openhole and cemented laterals, fracture stages with single and multiple cluster/ports, number of fractures/fracture spacing, and lateral length required to improve the production without compromising completion costs. To date, the benefit of the overall application has been a five-fold production increase and, as expected, a significant improvement in the recovery factor.
Pumping Balls: A Study on Flow Conditions for Frac Ball Launching and Conveyance
Authors: Dardis M. , Melenyzer G. , Aviles I. 
Published: June 2014

Abstract
The use of ball drop type fracturing tools has been instrumental in the increase of activity in hydrocarbon-bearing reservoirs. These systems rely upon a series of balls that increase in size to progressively isolate stimulated intervals from toe to heel. It is of extreme importance to predict the behavior of such balls as they are pumped into the flow stream and ultimately the completion to avoid undesirable over-flushing of the fracturing stage.
In order to better understand the dynamics of launching these balls, a full scale surface test was performed on a flow loop. Using a ball launching device, balls ranging in size from .795" to 3.0" and composed of magnesium, aluminum, or ceramic material were introduced into flow streams of varying rates. The flow rates were designed to mimic both the flow rate through the ball launching device and the total flow rate after rejoining the treatment line. Various conditions were simulated including competing rates as the balls traveled through a simulated treating line and standpipe.
Computer modeling was utilized to further understand the behavior of fracturing balls displaced by fluid in horizontal multistage completions. The change in fluid velocity through the balls seats was studied to simulate the pump rate necessary for a ball to travel through the completion and land on the intended seat to provide isolation.
The information gathered during this experiment was analyzed to determine optimum flow conditions required to successfully launch fracturing balls. The effect of the ball size and material was studied to determine what influence they had on the ability of the balls to travel with the fluid. Recommendations on minimum rate versus ball size will be presented for both surface and down-hole scenarios.
Laboratory Results of Proppant Transport in Complex Fracture Systems
Authors: Sahai Rakshit (Raki) , Miskimins Jennifer L. , Olson Karen E. 
Published: June 2014

Abstract
With a global paradigm shift towards exploring shale reservoirs, the industry focus has moved towards optimizing hydraulic fracturing in these reservoir types. Low-viscosity slickwater fracture treatments are commonly used as a completion technique in these ultra-low permeability reservoirs. Each shale reservoir is different due to the presence of in situ natural fractures and other geologic complexities, and thus the resultant hydraulic fracture network is distinct and the proppant transport in these "created" complex fracture networks is not clearly understood. Much speculation exists in the industry as to how efficiently the proppant is transported from the primary fracture into subsidiary fractures, if it is at all. A better awareness of proppant movement in complex fracture networks can possibly help with better hydraulic fracture treatment designs by focusing on parameters that enhance transport in the subsidiary fractures and understanding what impacts this transport may have on the resulting production.
This paper discusses a series of tests carried out in a low-pressure laboratory setting to evaluate proppant transport in complex fracture networks. Different slickwater treatment scenarios were simulated by pumping sand slurry through a series of complex slot configurations while varying the slot complexity, pump rate, proppant concentration, and proppant size. Results from twenty-seven tests carried out provide some interesting insights into the nature of proppant transport and settling in complex fracture networks. In the case of a primary slot system, the proppant transport was observed to occur via traction carpet after the creation of a proppant dune. However, in the case of secondary slots, the proppant transport was found to be dependent on the dune buildup in the primary slot. Two mechanisms were observed to be transporting the proppant into the secondary slots: 1) proppant flowing around the corner at pump rates higher than the threshold pump rate (related to the threshold velocity in the primary slot), and 2) proppant falling from the primary slot due to the effects of gravity, regardless of the pump rate.
Microseismic Estimates of Stimulated Rock Volume Using a Detection-Range Bias Correction: Theory and Case Study
Authors: Zhang X. , Holland M. , van der Zee W. , Moos D. 
Published: June 2014

Abstract
Microseismic monitoring is becoming an integral part of hydraulic fracturing. The observed microseismic events reflect the rock failure that occurs during or after the stimulation, and so the events’ spatial distribution is often used to determine the stimulated rock volume (SRV) and the event frequency is used to derive stimulation effectiveness. However, discrepancies are often observed between the production rate (or the flow rate) and the stimulation effectiveness computed using the observed microseismic event locations and frequency. This study presents a multi-step workflow for calculating stimulation effectiveness. The workflow is developed based on two observations. The first is the recognition that the attributes used for calculating stimulation effectiveness must be related to deformation. The second is that it is possible by using a method based on the parameters of the Gutenberg-Richter to correct for spatial detection bias. We first describe the workflow and then apply it to calculate stimulation effectiveness using a microseismic event data set obtained during multistage fracturing stimulation of an upper Devonian shale gas reservoir in southern West Virginia. The workflow provides an improved estimate of stimulated reservoir volume. The approach has been tested here using only the magnitudes and locations of the events. Further improvement is possible using moment tensor / focal plane solutions.
Changes in Shale Fracture Conductivity due to Interactions with Water-Based Fluids
Authors: Pedlow John , Sharma Mukul 
Published: June 2014

Abstract
A sizable amount of literature exists analyzing the effect of confining stress on fracture conductivity in sandstones. This report attempts to answer similar questions with regard to shale formations. The low Young's Moduli and Brinell hardness values characteristic of many prospective shale formations may lead to a great deal of embedment and fines production which can drastically reduce fracture conductivity. Furthermore, shales exhibit sensitivity to aqueous fluids which may cause them to be weakened in the presence of certain fracturing fluids. Previous work analyzing shale fluid sensitivity has failed to preserve the shales’ formation properties by allowing the shale to dry out.
This paper presents a study of propped fracture conductivity experiments at reservoir temperature and pressure using various North American shale reservoir cores. Exposure to the atmosphere can alter the mechanical properties of the shale by either drying or hydrating the samples, so care was taken to preserve these shales in their native state by maintaining constant water activity (relative humidity). Variations in applied closure stress and aqueous fluid exposure were analyzed and in certain cases altered the propped fracture conductivity by crushing proppant, embedding the proppant into the fracture face, and producing fines. The damage to fracture conductivity is correlated to mineralogy for the various shale samples. These findings show that a one-size-fits-all frac design will not work in every shale formation, rather a tailored approach to each shale is necessary.
In the future, the results of this work will be analyzed alongside easier to perform Brinell hardness tests, swelling tests, and other characterization techniques incorporated into the UT Shale Characterization Protocol (Zhou et al., 2013). Correlations were developed to relate the simpler tests to the fracture conductivity experiments will yield an easier method to determine the role embedment and fluid sensitivity have on post treatment fracture conductivity in shales.
Fracability Evaluation in Shale Reservoirs - An Integrated Petrophysics and Geomechanics Approach
Authors: Jin Xiaochun , Shah Subhash N. , Roegiers Jean-Claude , Zhang Bo 
Published: June 2014

Abstract
The identification of fracture barrier is important for optimizing horizontal well drilling, hydraulic fracturing, and protecting fresh aquifer from contamination. The word "brittleness" has been a prevalent descriptor in unconventional shale reservoir characterization, but there is no universal agreement regarding its definition. Here a new definition of mineralogical brittleness is proposed and verified with two independent methods of defining brittleness. Formation with higher brittleness is considered as good fracturing candidate. However, this viewpoint is not reasonable because brittleness does not indicate rock strength. For instance, fracture barrier between upper and lower Barnett can be dolomitic limestone with higher brittleness. A new fracability index is introduced to overcome the shortcoming of brittleness by integrating both brittleness and energy dissipation during hydraulic fracturing. This fracability index considers that a good formation for hydraulic fracturing is not only of high brittleness, but also requires less energy to create a new fracture surface. Therefore, the formation with lower fracability index is considered as a fracture barrier, while with higher fracability is considered as better fracturing candidate. Logging data from one well of Barnett shale is applied (1) to verify the principle of new brittleness and fracability index model; (2) and to demonstrate the process of screening hydraulic fracturing candidates employing fracability index model.
Mid-Continent Water Management for Stimulation Operations
Authors: Tipton D. Steven 
Published: June 2014

Abstract
Water is the most common and heavily used fluid in the petroleum industry. It is produced along with oil and gas from nearly every well. Fresh water is used as a base fluid in drilling, completion, and production operations. Produced water is handled in three primary ways: injected in salt water disposal wells, for pressure maintenance in secondary or tertiary recovery projects, or as a recycled base fluid in hydraulic fracturing.
In unconventional oil and gas operations hydraulic fracturing is the biggest user of fresh water. The focus of this paper is the procurement, conditioning, transportation, storage, reuse and disposal of water for hydraulic fracturing in Newfield's MidContinent operations.
Newfield's two primary fresh water sources are subsurface aquifers and surface water. The transportation of either fresh water or recycled (produced) water can be done by either pipeline or truck. Where possible it is preferable to transport the water through pipelines. For the transportation of smaller volumes of water 3" or 4" poly pipe is used or the water is trucked. Large volumes of fresh water are generally moved through 10" aluminum irrigation line, although polyvinyl chloride (PVC), lay flat hose, and high density polyethylene (HDPE) are also used. For the transportation of recycled or produced water HDPE has been the choice for most operators.
Newfield's preference for storing fresh water is unlined ponds because they can then be used by a landowner for long term water supply on his or her property. Lined pits are used where the soil conditions will not prevent water from leaking out. Fresh water can also be stored in frac tanks (500 bbl), modular tanks (up to 60,000 bbl), or portadams (sized as required). Recycled or produced water is stored in permitted lined pits, frac tanks, modular tanks, or portadams.
After fracturing a well, the produced water used can be recovered, stored, and reused. If the produced water cannot be reused it will be disposed via deep well injection (most common disposal method) or evaporation (limited use). The amount of produced water recovered after stimulation is dependent on the formation characteristics. Usually from 20 to 80% of the water used during the fracturing operation is recovered within the first 60 days of production and can be reused. Depending on the quality of the produced water recovered, it may require some type of treatment prior to reuse. Newfield began recycling water in its Wheeler County, Texas operations during 2005 because it made economic sense and the company is committed to responsible environmental stewardship.
A Methodology for Statistical Propped Fracture Treatment Design in Fluvial Environments
Authors: Smith P.E. , Dunn-Norman S. , Smith M.B. 
Published: June 2014

Abstract
Hydraulic fracturing treatment design historically has been deterministic in nature. In a deterministic design, the required design variables are single-valued and can be established with a reasonable degree of certainty. Additionally, their values are assumed to be laterally continuous. Fulfilling these assumptions is complicated for geologic settings in general, but nearly impossible in fluvial geologic environments, which violate the assumption of lateral continuity.
Recent work has defined a methodology for hydraulic fracturing treatment design using statistical methods to account for the complexity and heterogeneity in fluvial environments. The methodology demonstrates how to use statistics to address treatment design questions such as, “What is the vertical fracturing interval needed to create a well-confined, economical and productive fracture treatment in a highly layered, fluvial environment?” and “What is the optimal fracture treatment in such complex geology?”
This paper presents and describes the statistical-based hydraulic fracturing design methodology, including constructing and calibrating a basic geological model, incorporating geostatistics for the selection of alternate geological models, forecasting production for alternate fracturing treatments, and determining an optimum hydraulic fracturing design using all available information. The methodology is illustrated using geological and well data from a producing fluvial tight gas formation, though the approach should apply to other complex geological settings.
This work is valuable as it demonstrates a method for extending the deterministic approach taken with formation characterization and applying it directly to hydraulic fracturing design (thus, using the data where good values are available) to include statistics, thereby providing a basis for selecting an optimum treatment design when a range of possible design parameters exists for less well defined variables.
Pressurized-Fracture Propagation using a Phase-Field Approach Coupled to a Reservoir Simulator
Authors: Wick Thomas , Singh Gurpreet , Wheeler Mary F. 
Published: June 2014

Abstract
Tight gas and shale oil play an important role in energy security and meeting an increasing energy demand. Hydrualic fracturing is a widely used technology for recovering these resources. Prediction of fracture growth during slick-water injection and final geometry for single and muti-stage hydraulic allows quantitative assessment of frac-job scenarios. A recently introduced phase-field approach for pressurized fractures in a porous medium offers various attractive computational features for numerical simulations of cracks such as joining, branching, and non-planar propagation for heterogeneous porous media. In this study, we employ the phase-field fracture propagation model is used as a pre-processor in order to couple it to a fractured poroelastic reservoir simulator. This offers the possibility to simulate the entire scenario from hydraulic fracturing to the production process. The proposed algorithm is based on a one-way coupling and is therefore easy to adapt to existing legacy reservoir simulators. The phase-field model can be seen as a fracture-well-model in the reservoir simulator. The key idea behind this strategy is the possibility to couple reservoir and fracture flow in the phase-field formulation from which we obtain an initial condition for the reservoir simulator. Our proposed framework is substantiated with several numerical tests in two- and three dimensions.
Poroelastic versus Poroplastic Modeling of Hydraulic Fracturing
Authors: Wang Han Yi , Marongiu-Porcu Matteo , Economides Michael J. 
Published: June 2014

Abstract
With the increasing wide use of hydraulic fractures in the petroleum industry it is essential to accurately predict the behavior of fractures based on the understanding of fundamental mechanisms governing the process. The prevailing approach for hydraulic fracture modeling relies on Linear Elastic Fracture Mechanics (LEFM). Generally, LEFM that uses stress intensity factor at the fracture tip, gives reasonable predictions for hard rock hydraulic fracturing processes, but often fails to give accurate predictions of fracture geometry and propagation pressure in soft/unconsolidated formations. The reasons are that the fracture process zone ahead of the crack tip, elasto-plastic material behavior and strong coupling between flow and stress cannot be neglected in these formations. Recent laboratory testing has revealed that in many cases fracture propagation conditions cannot be described by traditional LEFM models. Rather, fractures develop in cohesive zones. In this study, we developed a fully coupled poroelastic and poroplastic hydraulic fracturing model with cohesive zone method which is able to model crack initiation and growth considering process zone effects. The impact of formation plastic properties on fracture process is investigated for both short term and long term injection and the results are compared with elastic formation. In addition, the main factors that affect the poroelastic backstress and the effects of formation plasticity on a hydraulic fracture are also investigated. The results indicate that both poroelastic backstress and formation plasticity lead to higher net pressure, but they have an opposite impact on fracture geometry. Poroelastic backstress tends to reduce fracture width while formation plasticity tends to increase fracture width. It was also observed that plasticity can reduce closure pressure below minimum horizontal stress. Poroelastic backstress is mostly controlled by the leak-off rate and formation permeability and the effects of plasticity are mostly influenced by in-situ stress, plastic properties and pore pressure. We also found that the effective toughness method which is used to quantify fracture process zone effect in soft formation tends to underestimate the fracture width and overestimate fracture length even if it can match the net pressure. Ignoring plasticity in certain formations can lead to inaccuracy of fracture geometry, net pressure prediction and fluid efficiency calculations. The deviations of real fracture geometry from elastic formation model can have great impact on well production, especially in unconventional, low-permeability reservoirs. So for a more accurate modeling of fracturing in plastic formation, the whole affected region around the fracture should be considered, especially when the plastic deformation area is large.