bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigation of Combined Electromagnetic Heating and Solvent Assisted Gravity Drainage for Heavy Oil Recovery
Authors: Hu Lanxiao , Li Huazhou Andy , Babadagli Tayfun , Ahmadloo Majid
Published: May 2016

Electromagnetic (EM) heating holds a large potential in heavy oil recovery since it can reduce carbon emission and avoid excessive water usage, and is applicable for water hostile reservoirs such as shale oil reservoirs. Combining solvent injection and EM heating might further reduce the energy intensity of the process. The merits of using solvent in EM heating include diluting heavy oil and thereby increasing its mobility, serving as a heat carrier by reinforcing heat convection in porous media and facilitating gravity drainage by forming a vapor chamber. Detailed experimental investigations are needed to investigate the mechanism of such a complex process and to specify the most influential factors of this hybrid and expensive process to determine optimal operational conditions. In this study, we conduct a series of laboratory experiments to investigate the mechanisms of combined EM heating and solvent assisted gravity drainage for heavy oil recovery.

During experiments, sand pack samples contained in Buchner filter funnel are placed in a microwave oven. Solvent injection can be initiated together with EM heating to simulate the hybrid process of combined EM heating and solvent assisted gravity drainage. We investigate the effects of influential factors on the process efficiency, including initial water saturation, solvent types (n-hexane and n-octane), introduction methods of solvents (injection or premixed with oil), combination strategies of solvent injection and EM heating (simultaneous or alternate means), and EM heating power. Temperatures of the sand pack and oil recoveries are simultaneously recorded. Experimental results show that combined EM heating and solvent assisted gravity drainage could effectively enhance heavy oil recovery compared with EM heating or solvent use alone. A higher heating power provides a faster temperature rise and earlier oil production in the sand pack. Moderate initial water saturation could increase the heating speed, leading to a higher oil recovery. Solvent injection can further enhance the viscosity reduction and swelling effect of heavy oil due to EM heating. Compared with n-hexane, n-octane provides higher vertical displacement efficiency and oil recovery under the same experimental conditions. Alternate EMH and solvent injection is more cost effective due to the lower energy consumption compared to the simultaneous EM heating and solvent injection.
Temperature-Dependent Deformation Prediction of Oil Sand by Coupled Geomechanical and Fluid Flow Modeling
Authors: Kashihara Koji , Rutqvist Jonny
Published: May 2016

Reservoir deformation during steam injection of SAGD operation can result in the increase in formation permeability that can positively impact to the bitumen production. The reservoir deformation behavior is controlled by the mechanical properties of oil sand, which are highly dependent on temperature. This work is focused on the temperature dependency of elastic properties of oil sand and its impact on geomechanical responses during a SAGD operation. Coupled geomechanical and fluid flow modeling technique is employed to illuminate the impact of the change in elastic properties to the reservoir deformation behavior.

Rock physics modeling is conducted at first for quantifying the temperature effect on the elastic properties of oil sand. Based on the investigation of log data from an actual SAGD operation field, we used the soft-sand model to calculate dry-frame elastic properties of the unconsolidated sand. We then applied and investigated several substitution methods to quantify the effect of the pore-filling bitumen on the elastic properties of the oil sand. We selected one of the solid substitution methods instead of Gassmann equation because bitumen behaves like solid at low temperature. The coupled hydraulic, thermal, and geomechanical simulator, TOUGH-FLAC, is used to investigate the effect of oil sand's elasticity on reservoir deformation behavior. The coupled modeling for SAGD is conducted for two simple cases; one case with the elastic properties at original reservoir temperature and the other case with the updated elastic properties considering the increased temperature. Comparison of the results from the two cases demonstrates the importance of considering the effect of temperature on the elastic properties of oil sand. This work is new in terms of combining rock physics modeling for quantitative description of the oil sand elastic properties and the coupled hydraulic, thermal, and geomechanical modeling considering the temperature-dependent elastic properties of oil sand.
Experimental Research on Thermal Cracking of Mudstone for Heavy Oil Thermal Production
Authors: Sun Feng , Xue Shifeng , Wang Haijing
Published: May 2016

Thermal production is an important heavy oil recovery method. While production, Steam injection triggers complex thermal and hydraulic processes which can dramatically alter the formation pressure and temperature leading to various changes within the reservoir as well as in the surrounding rock. This study is conducted to experimental research on the thermal cracking characters of mudstone barriers induced by heavy oil thermal production.

In this research, a thermal-mechanical coupling experimental device was developed. It can impose triaxial stresses and local wellbore high temperature to the rock sample. The temperature sensor was used to record the temperature change in the rock sample. Industrial computerized tomography (CT) technology was employed to scan the rock sample before and after the experiments, compared the changes of CT images and observe the thermal cracking characters of mudstone.

Mudstone of our laboratory studies were coring from the heavy oil reservoirs of Xinchun Oilfield (Xinjiang, China). The experimental results are listed as follows: (1) The thermal cracking developed with heating temperature increase. It's observed that the micro-fissures developed and connected to form larger fractures under 260°C. (2) The fractures propagate along the maximum/minimum horizontal stress direction on the surface of rock sample. CT images indicated that fractures propagation along the horizontal stress direction inside the sample. The propagating patterns also affected by the rock lithology, natural fissures and formation heterogeneity, etc. (3) The width of thermal cracking change with temperature, and the fractures closure during cooling from the growth temperature of 260°C to room temperature.

The above works show that thermal production affect the deformation and failure behavior of the mudstone barriers, it may cause the thermal cracking during multiple steam stimulation process. This will be instructive for optimizing the parameters of thermal production.
Accuracy and Reliability of a New-Generation Optical PT Gauge in a SAGD Field Trial
Authors: Ficocelli Peter , Baldwin Christopher , Vincelette Andre , Luckanachai Praise
Published: May 2016

Accurate and reliable subsurface pressure and temperature (PT) measurements facilitate SAGD production improvements. The dynamic nature of the SAGD process requires real-time control of subsurface temperature and pressure to better manage subcool and steam-oil ratio (SOR). With SAGD operating temperatures in excess of 250°C (482°F), the use of several fiber optic sensing technologies have been explored for more than a decade with variable results. The successful implementations are designed with proven optical technologies that can operate in the harsh and aggressive SAGD operating environments. Fiber Bragg grating (FBG) based array temperature sensing (ATS) and glass Cane™ technologies have been field proven to withstand ultrahigh temperature and hydrogen-rich SAGD environments.

We describe the unique aspects of fusing FBG and glass Cane technologies to provide a stable sensor for such harsh conditions. Qualification testing of the Cane-based optical PT gauge for accurate and reliable subsurface measurements and the results and analysis of the field trial are also presented for the initial 12-month period covering the conditioning and production phases.

The lab qualification and test plans are presented to validate the specifications of the optical Cane PT gauge designed for all SAGD operational conditions. The lab tests consisted of multiple thermal and pressure cycling, vibrations, and shocks. The performance of the gauge during the field trial is also described. The conditioning period provides an excellent reference point to validate the quality of the co-located pressure and temperature values reported by the PT gauge installed at the toe of the well. The gauge temperature and pressure readings are compared to surface readings and subsurface saturated steam conditions. Temperature and pressure readings at the toe of the well during the production phase are analyzed and compared to intake pump pressure measured using a reputable, earlier-generation, optical PT gauge.

The glass Cane PT gauge provides improved reliability and accuracy because of the novel rigid internal structure of the device that preserves the slimline 1/4-inch external diameter. The increased accuracy of the measurements enables operations at a lower subcool, thus increasing production while lowering cSOR. The increased thermal and pressure range allows short bursts of extreme-high-pressure fluctuations and operation in cyclic steam stimulation (CSS) and other thermal applications.
Completion and Well Spacing Optimization for Horizontal Wells in Pad Development in the Vaca Muerta Shale
Authors: Suarez M.. , Pichon S..
Published: May 2016

In organic shales, hydraulic fracturing is an important parameter to optimize production of horizontal wells. For a lateral standalone, propped surface should be maximized to increase production (by increasing total proppant per well). While in the case of a pad, well spacing is an additional constrain for hydraulic fracture dimensions not to overlap with hydraulic fractures of neighboring offsets. Competition for production between laterals of a given pad should be minimized and is the result of both well spacing and hydraulic fracture design.

A numerical model coupling an explicit description of the hydraulic fracture geometry and reservoir simulation is proposed. Fracturing simulator accounts for material balance, geomechanics, interaction with natural fractures and stress shadowing within and in between fracturing stages.

Production interference is evaluated by comparing forecasted production of a lateral standalone (single well approach) against this same lateral while surrounded by offsets competing for production (multi well approach). Sensitivities are run assuming different completion and well spacing scenarios varying different parameters such as fluid and proppant volume, fracturing fluid type and staging.

Production interference between horizontal wells might reduce the final recovery of each individual well. However it provides an opportunity for simultaneous optimization of completion and well spacing to guide field development.

Hydraulic Fracture dimensions must match well spacing. Variation of fracture geometry along the lateral should be accounted for to evaluate well spacing and prevent the excessive growth of one single facture within a given stage. Completion design can be engineered by adjusting hydraulic fracture treatment volume, perforation cluster spacing or fracturing fluid viscosity to increase the overall consistency of the resulting fracture geometry and reduce effect of production interference between laterals of a given pad.

Novelty of the proposed methodology relies on the explicit description of the hydraulic fracturing geometry and direct coupling with reservoir simulation, not only for a single well, but considering a whole pad of horizontal wells as per a possible development of the Vaca Muerta shale.
Stimulation Optimization Using Engineered Diversion Workflow to Increase Wellbore Contact in Cemented Completions
Authors: Heaton N.. , Rondon J.. , Do T.. , Valenca A.. , Bruns J.. , Ohlson C.. , Eisele K.. , Paneitz J.. , Rollins B.. , Betts B.. , Cleaver Sarah
Published: May 2016

Completion techniques in the Middle Bakken formation have evolved over the years, with cemented Plug & Perf becoming the most common technique in recent years. It relies on stimulation of multiple clusters of perforations, normally 3-5, at one time. As previously demonstrated by multiple papers (SPE 173363, 144326, 167726, 174943) up to 40% of the perforation clusters remain un-stimulated. A novel engineered diversion workflow was implemented in 687 intervals of 20 Williston Basin wells. The purpose of this workflow is to increase cluster efficiency by stimulating the previously un-stimulated clusters. Results from each step down test and engineered workflow evaluation indicate increased cluster efficiency by up to 80%. Moreover, the success criteria for diversion pressure (1000 psi) was achieved on 81% of the intervals. Due to the success of these wells, this workflow has now become the standard diversion technique for one major operator in the Williston Basin.
A Utility Discrete Fracture Network Model for Field-Scale Simulation of Naturally Fractured Shale Reservoirs
Authors: Mi L.. , Jiang H.. , Tang L.. , Liu C.. , Li J.. , Wang Y.. , Cao Y.. , Killough J..
Published: May 2016

Multi-scale fracture distribution is a unique feature in shale gas reservoirs development. For a reservoir engineer, establishing a utility method which can be both numerically efficient and practically accurate is the greatest challenge of shale gas reservoirs numerical simulation.

Naturally fractured shale gas reservoirs, which must be fractured before production, include many complex fracture networks (natural fracture and hydraulic fracture) that cannot be easily modeled by the simple continuous medium model (CMM), the discrete fracture model (DFM) or the discrete fracture network (DFN) model. In this paper, we propose a utility discrete fracture network (UDFN) model in which natural fractures are modeled by an analytic correction to matrix permeability, and hydraulic fractures are modeled by the DFN in which fractures are modeled explicitly. The partial differential equations are solved by Newton Raphson method through the C Sharp programing.

Case studies reveal that the UDFN's computational speed improves orders of magnitude than those of the DFN and DFM when dealing with the same problem, while the numerical result from UDFN method keeps enough accuracy to match the production curves as well as the results from the DFN. Meanwhile, the UDFN not only can simulate individual fracture's effects explicitly like DFM, but also can match up better to the field production than the DFM.

The method developed in this paper improved the simulation of multiple stage fractured horizontal wells performance in naturally fractured formations. It also makes the naturally fractured shale gas reservoirs numerical model much more concise and practical to the field case appplication.
Estimating Anisotropic Mechanical Properties and Stress Based on Measurements on Cuttings for Completion Quality: Methodology and Case Study in Vaca Muerta
Authors: Prioul R.. , Frydman M.. , Caniggia J..
Published: May 2016

Unconventional plays such as Vaca Muerta are geologically complex and heterogeneous. Wells must be hydraulically fractured to produce, and material fabric, material properties, and in situ stress strongly influence this process. When logs are not available in the laterals, measurements on drill cuttings can be used to estimate anisotropic mechanical properties and stresses. The proposed method relies on two main steps. First, using one or more data-rich pilot wells, we define and calibrate rock physics and geomechanical models. The rock physics model provides the necessary relationship between the petrophysical volumes (mineralogy, organic matter and fluids) and the elasticity moduli, and the geomechanics model the relationship between elasticity moduli and the stress indices and the minimum stress. Second, in nearby lateral wells, we measure mineralogy and organic matter on cuttings samples using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and apply the models to compute the elastic and stress properties. We illustrate this method using two vertical pilot wells that cross the Quintuco and Vaca Muerta Formations, Argentina, and one horizontal lateral well in Vaca Muerta. A complete suite of petrophysics logs have been acquired in both pilots, in addition to DRIFTS measurements on cutting samples in one of them and rock mechanics lab measurements on cores in the other one. In the lateral well, DRIFTS data have been acquired. We limit this paper to the construction, calibration and application of the rock physics model, as the construction and calibration of the geomechanical model is reported in a companion paper. We show that the sonic moduli can be reconstructed very accurately from the petrophysical volumes in the Quintuco and Vaca Muerta formations. The rock physics model highlights the impact of the high TOC in Vaca Muerta and of the mineralogy in Quintuco. The anisotropic shear moduli of Vaca Muerta are also predicted satisfactorily. To demonstrate the methodology, DRIFTS measurements on cuttings from the pilot well, are used to predict the sonic-derived moduli. Despite the sampling of the cuttings every few meters compared to the log data every 15 cm, we show an excellent consistency between DRIFTS- and log-derived elastic moduli. The model is then applied to DRIFTS data acquired on cuttings in a lateral, and the cutting-derived stress indices are computed. This method is both practical and theoretically sound. First, deterministic rock physics and geomechanics models are calibrated with high-resolution log data in a pilot well to relate petrophysical volumes to stress properties. Second, the use of spectroscopy logs in pilots and spectroscopy measurements on cuttings in laterals allow accurate estimation of stresses using cutting-based measurements in data-lean environments.
Case History: Hybrid Completion Method Employed for Longest Horizontal Unconventional Well in Vaca Muerta, Argentina
Authors: Welch M.. , Allen R..
Published: May 2016

Argentina possesses some of the largest shale oil and gas reserves in the world and has the potential to benefit from the technologies currently used to extract unconventional shale resources in North America. Historically, Vaca Muerta resources were produced using vertical wells that were often stimulated in a few zones with plug-and-perf technology. Recently, operators started to adopt horizontal drilling and new multistage completion technologies to maximize access to the reservoir and increase production.

Although vertical wells are still popular, horizontal wells are gaining popularity in Argentina. Operators experimenting with horizontal wells are drilling longer laterals and are increasing the stage count within those laterals. Plug-and-perf is the typical completion system in horizontal wells; however, new technologies such as ball-activated sliding sleeve systems are being tested.

This paper will present the unconventional multistage hybrid completion of an exploratory well in the Neuquén Basin targeting the Vaca Muerta formation. The completion was comprised of 28 total stages: 13 open-hole, ball-drop sliding sleeve stages in the lower portion and 15 cemented plug-and-perf stages in the top portion. Disintegrating ball technology was used in conjunction with sliding sleeves so that post-frac intervention was eliminated in the deepest part of the well. The plug-and-perf stages were milled out after the fracturing treatment.

This well was the longest lateral drilled to date in Argentina at 2,016 meters (6,614 feet) and had the highest initial production rate of any well in Argentina's history. The lessons learned from this well can help Argentinian producers select the best completion method for large-scale development of unconventional resources in the Vaca Muerta Shale.
Is Induced Fracture Complexity Always Required in Unconventional Reservoir Stimulation?
Authors: Sierra Leopoldo
Published: May 2016

Induced fracture complexity maximization, in addition to the primary hydraulic fracture, to improve the recovery efficiency or productivity of gas or liquids in unconventional resource shale reservoirs has been accepted and fully implemented by the industry. As a result, stimulation fluids and/or completion strategies have been engineered to maximize induced fracture complexity in many unconventional reservoirs. In typical unconventional horizontal completions, induced fracture complexity is beneficial for the productivity of nanodarcy (nd) shales if conductivity is sustained in time, although induced fracture complexity may not be a requirement for all unconventional reservoirs, especially tight sands.

In some unconventional reservoirs, operators have observed similar productivity in wells with predominantly planar fractures compared to wells that appear to have more complex fractures. This paper, supported by extensive reservoir simulations, aims to develop criteria for situations in which induced fracture complexity and sustained conductivity are required and when they are not. The simulations include a reservoir permeability range of 10 nd to 0.001 md and a fracture complexity conductivity of 1 to 5 md-ft with and without stress dependence. The simulation results show that the fracture complexity with a constant and sustained conductivity (no stress dependent) are generally important for reservoir permeabilities lower than 100 nd for gas and 500 nd for liquid-producing reservoirs, but this benefit is minimized when the induced or existing stresses negatively affect the fracture complexity conductivity.

Based on these results, an optimized completion strategy is suggested to maximize the productivity or recovery factor (RF) in unconventional gas- and liquid-producing reservoirs.
Reservoir Flow Regime Assisted Multi-Segment Production Forecasting
Authors: Jeyachandra B.. , Sharma A.. , Dwivedi P.. , Gupta S..
Published: May 2016

In many companies, production forecasting using multiple segments is gaining traction. Theoretically, the multiple segments are used to capture the different flow regimes in the reservoir over a period of time. A three-segment Arps decline model has been prevalently used, where, in early time, an Arps b parameter of 2 is used to denote transient flow;, during middle time, an b parameter of 0.2 to 1 is used; and, during late time, a b parameter of 0 to 0.2 is used to denote the boundary dominated effects. Choosing the segments and the b parameters was usually based on an educated guess about the reservoir and the visual observation of the changing slopes of decline.

The three-segment model presupposes a reservoir behavior that may not be happening in the field, and varying operating conditions can skew the production rate slope and can mask the flow regimes observed in the reservoir, This, in turn, can lead to misleading forecasts. We are proposing a way to remove the guesswork from flow transition, the presupposition of flow regimes in the reservoir, and the masking effects of pressure using rate transient analysis.
Analysis of Enhancement Shale Gas Recovery by CO2 Storage
Authors: Tang L.. , Sun S.. , Mi L.. , Wang L.. , Qi H.. , Yu R.. , Bai F.. , Chaoyang J..
Published: May 2016

In order to enhance shale gas recovery and store CO2 geologically, a development model of EGR by CO2 flooding in shale was proposed based on the thought of CO2 flooding oil. In order to investigate the potential of EGR by CO2 flooding, experiments in house and simulations of well pattern were carried out. Specifically, In-house study included experiments of adsorption isothermal between CH4 and CO2 and experiments of displacement seepage CH4 by CO2. The results of above experiments show that, adsorption capacity for CO2 was about three to five times than that for methane in shale formation at the same condition of pressure and temperature. In addition, gas recovery for adsorbed gas would be promoted more than 20% just because of CO2 flooding CH4 during displacement experiments in question. What was more, it was found that two main mechanisms for CO2 EGR in shale gas were concluded as molecular replacement by CO2 and keep of formation pressure by CO2 injection. Based on the results of experiments, considering difficulty of CO2 injection due to poor property of shale formation, this paper proposed a solution of CO2 injection in one well and production shale gas in two wells nearby based on the ideas from well pattern of water flooding oil in oil field. Distance between injection and recovery can be calculated by theory calculation, providing references for carbon dioxide flooding in the field.
Data Driven Production Forecasting Using Machine Learning
Authors: Cao Q.. , Banerjee R.. , Gupta S.. , Li J.. , Zhou W.. , Jeyachandra B..
Published: May 2016

Forecasting of production in unconventional prospects has gained a lot of attention in the recent years. The key challenges in unconventional reservoirs have been the requirement to put online a) a large number of wells in a short period of time, b) well productivity significantly driven by completion characteristics and that c) the physics of fluid flow in these prospects still remain uncertain. In this paper, machine learning algorithms are used to forecast production for existing and new wells in unconventional assets using inputs like geological maps, production history, pressure data and operational constraints. One of the most popular Machine Learning methods – Artificial Neural Network (ANN) is employed for this purpose. ANN can learn from large volume of data points without assuming a predetermined model and can adapt to newer data as and when it becomes available. The workflow involves using these data sets to train and optimize the ANN model which, subsequently, is used to predict the well production performance of both existing wells using their own history and new wells by using the history of nearby wells which were drilled in analogous geological locations. The proposed technique requires users to do less data conditioning and model building and focus more on analyzing what-if scenarios and determining the well performance.
Enhancing Well Performance via In-Stage Diversion in Unconventional Wells: Physics and Case Studies
Authors: Fragachán F. E. , Shahri M. Pordel , Arnold D. M. , Babey A. G. , Smith C. S.
Published: May 2016

Production rates in unconventional plays can decline dramatically, up to 70% in the first year. Refracturing—by today's understanding—is a remedial production operation often done because original fracturing failed to contribute any significant amount of flow, performance of the initial completion has degraded over time to below operationally or economically acceptable limits, or significant unfractured pay exists in the well.

Developments in nondamaging, degradable diverters with outstanding plugging efficiency have opened new opportunities for protecting existing fractures by plugging them and then fracturing zones that were previously bypassed because of inefficient zone coverage or refracturing zones that were inefficiently fractured initially. In fact, these new diverters enable zonal isolation for horizontal wells with multiple perforation clusters and for temporarily plugging perforations for re-stimulation treatments instead of squeezing the perforations and sealing them off. With multistage operations becoming the industry norm, operators need easily deployable diversion technologies that will protect previously stimulated perforations and enable adding new ones to untreated perforations or bypassed zones.

This paper reviews in-stage Diversion, including a brief discussion of diverter candidate selection in terms of production and risk assessment to ensure return on investment. Also included is an explanation of underlying mechanisms controlling the diversion process and the use of advanced modeling techniques to enhance efficiency of diversion operations. Then a case study is discussed to highlight how temporary and degradable chemistry can be used to enhance zone coverage, to provide temporary isolation between zones in shale fracturing operations, and to achieve multiple effective fracture treatments within the same stage. These degradable chemical diverting agents form a solid impermeable barrier or seal that in time will break or degrade to liquid form, leaving the existing zone that was diverted open to permit flow.
Multi-Well Stimulation Optimization in Shale Formation: Modeling and Application
Authors: Xu Ben , Li Yanchao
Published: May 2016

In order to increase production rate, reduce treatment period, and solve some special problems, multi-well completion has been proposed, especially in mountain areas with limited well pads. Simultaneous fracturing and zipper fracturing are two new fracturing patterns in multi-well completion, which can increase fracture network complexity and stimulated reservoir volume (SRV) because of the interference of wells or fractures. However, unlike multi-frac treatments of a single well, interference between multi-wells also increases difficulties on hydraulic fracturing design.

In the previous papers, we have shown that natural fractures impacted the direction of hydraulic fracture propagation and mechanical properties of reservoir formations, which increases the complexity of fracture network complexity. As known, hydraulic fracture propagation is a complicated process influenced by frac spacing, hydraulic fracture length, mechanical properties of natural fractures, and in-situ stress. Especially, in-situ stress and natural fractures play more complex roles in multi-well completions.

In this paper, we presented one numerical model to better understand the process of hydraulic fracture propagation in multi-well completions, which includes influences of in-situ stress changes and interactions between hydraulic fracture and natural fractures. The numerical results show that in addition to hydraulic fracture propagating, natural fracture opening also changes in-situ stress, which makes hydraulic fracture network more complex. The model has been validated in a zipper fracturing case, and the optimization of well spacing, frac spacing and treatment volume has been proposed to enhance stimulated reservoir volume (SRV) and increase shale gas production.

The simulation results of this paper provide some guidelines for hydraulic fracturing design in multi-well completions, which contains optimum well spacing, frac spacing, and treatment volume. The results of this paper may also help deal with limited well pad area and increase gas production, and ultimately it should lead to improved well economics.
Hydraulic Fractures Behavior Evaluation in Vaca Muerta Formation, Case Studies
Authors: Moreyra J. D.
Published: May 2016

The objective of this work is to show that the estimated stimulate reservoir volume (SRV) from micro seismic analysis under dynamic conditions not always represents the SRV acting as hydrocarbon collector and need to be calibrated with total organic content (TOC), vertical and areal distribution. Furthermore, unlike conventional reservoirs, the potential leakoff damage caused during the fracturing and the SRV generation process, are not detectable by pressure transient analysis (PTA), but us a change on SRV transmissibility.

Integrating PTA, net pressure behavior during fracture treatment and micro seismic analysis results, allow us to better understand the reason that seismic events from one or more monitoring wells, might conduct us to wrong interpretation of the active SRV. Field cases show how PTA conventional technique helps to identify the existence or absence of an effective SRV connected to each individual hydraulic fracture stage and its associated best quality TOC thickness.

Results confirm that active SRV, generated by hydraulic fracture treatment in lower Vaca Muerta, where the seismic events practically are no detected, PTA analysis has an excellent infinite conductivity fracture behavior on the best TOC thickness. Production potential depends on different factors, net pay with TOC percentage greater than 2.5 %, vertical and areal distribution associated to rock porosity, natural fissured and SRV are the most important parameters. It is critical to understand the system deliverability potential, it must be evaluated under production conditions and the active SRV adjusted with TOC percentage and distribution, taking into account the effects caused by SRV pore pressure drop. Network of natural fissures originally in place and changes generated around the main fracture, combine to enhance the quality system.

An improvement of active SRV transmissibility was detected after the buildup period, increasing from 20 to 80 % oil production and more than three times the initial production. As in conventional reservoirs, where pressure test results are related to formation transmissibility, in unconventional reservoir pressure test results are related to SRV transmissibility and TOC percentage.

It can be concluded that the best zones to be fractured are determined by PTA associating to logging and cutting geochemistry analysis. PTA evaluation will determine only chocked fracture damage and not surface fracture damage.

PTA allows us to improve well completions efficiency and amount of fractures. Vertical wells production performance and best zones knowledge, will allow a better choice of zones to be developed thru drilling horizontal wells. In spite of industry belief, PTA analysis can give us a better understanding of SRV behavior in contact with the generated primary fracture.
Conventional Fracturing vs. Complex Fracturing Network in Tight Turbidite Oil Deposits in Mexico
Authors: Murillo G. Gutierrez , Salguero Javier
Published: May 2016

Over the past decade the hydraulic fracturing industry has been working to increase oil production from low-permeability or "tight" sands formations by applying the experience and techniques gained from shale oil and gas well completions. The shale-based completion approach calls for the creation of complex but short-length fracture networks via the use of low-viscosity fluid systems combined with pumping at higher rates than a conventional stimulation. This paper is a case study of an oil-producing basin in Mexico. It evaluates the impact on cumulative production from stimulations assumed to have a greater fractured length compared to stimulations of the complex fracture network type with their associated shorter fractures. This paper uses data from a 13-year period (2003 to 2016) comparing wells in two tight sands fields with varying characteristics such as well design, vertical and horizontal configuration, fracture fluid systems and completion techniques.

Due to the studied fields' petrophysical characteristics, hydraulic fracturing was necessary in all cases to economically produce hydrocarbons. Beyond this common characteristic, key properties varied across fields, with high heterogeneity due to the characteristics of the turbidite reservoirs. Natural fractures were not always present, permeability varied from 0.3 to 5 mD, while average porosity was 15% with low changes in vertical stress. Microseismic data acquired in the Basin provided information critical to understanding fracture behavior and, when combined with fracture simulation software, estimating propped geometry.

Among the central observations of this study is that the stimulated reservoir volume (SRV) has certain limitations when oil-bearing compact turbidites are being stimulated. This was especially observed in lateral wells where the minimum horizontal stress (Shmin) increased gradually towards the heel of the well, making it more difficult to generate a complex fracture.

The study area's stimulated wells showed a strong correlation between fracture half-length and cumulative hydrocarbon production. This proved true even among wells with complex fracture networks that typically had higher initial production. The critical conclusion of this study is that an oil well in low-permeability compact turbidites with greater fractured length can generate cumulative production up to 60% greater than a well with a complex but shorter half-length fracture network.
Main problems of stability and change in tradition
Authors: Bascom William
Published: May 2016

With the effects of acculturation to be seen in all parts of the world, we may have to be reminded how recently its importance has been recognized. The twentieth century has brought us face to face with change, but the fact about culture which was most obvious in the last century was its stability. Some cultures had existed with little change over many centuries, and others had been spread through colonization to new parts of the world where they persisted despite considerable geographical differences. There was a tendency to take cultural stability for granted, though it was recognized that changes could result from migrations and conquests. The Tylorian theory of cultural evolution, developed only toward the end of the century, held that societies progressed from one stage to another as the result of internal change, but the manner in which these changes came about was almost mystical and inevitable. Other scholars seriously maintained that primitive peoples lived in “cultural straight jackets” which prevented change and, indeed, even individual variation in behaviour. It was widely believed that human behaviour was biologically determined, and that certain people were musical or amusical, or rhythmical and incapable of harmony, by virtue of their race. Learning as a means of cultural change had little place in these theories, and in the light of what we know today the important mechanism of cultural borrowing was completely underrated. It is sometimes hard to realize that the fact that folktales can and do diffuse from one place to another, without the agency of migration, had to be proved within the last hundred years.
On transcribing African music
Authors: Jones A.M.
Published: May 2016

There are two standpoints from which to survey African music. One is the impressionist point of view. This seeks to evaluate the total effect of the music on the listener or the performer. It is concerned more with quality than with detail; with descriptions of the people and the instruments engaged in making the music and the sort of sound they produce. It is an aesthetic approach and is therefore essentially subjective in character. It attempts to answer the question ‘From the musical point of view, what is to be said about African music? Is it beautiful? Is it colourful? Is it rhythmically virile? What does it sound like?’ Such an approach has its value and yet by itself it can never reveal African music to the world. The reason is that it concentrates on the effect of the music produced and does not seek to discover the way it is produced. Were the fundamental techniques of African music-making the same as those used by the observer there would be no point in this latter inquiry. But if they are not, then in order to apprehend this music it is essentially to study not only its aesthetic aspects, but also, and we would say predominantly, the exact techniques used in producing it. In contrast with the impressionist, this is the analytical point of view.
Towards an assessment of African scales
Authors: Tracey Hugh
Published: May 2016

It would appear from the evidence of certain writers on African music that there still remains much confusion about the subject of African scales and modes. A tenacious misconception continually occurs, namely that African scales or modal systems are but an imperfect imitation of, or striving towards, the western system. Nothing, of course, could be further from the truth. It is with the intention of opening the subject for discussion by members of the Society and others interested in this aspect of musicology throughout the African world that this short article is now written. In order to avoid a confusion of terms which would take too long to enumerate here it might be as well for the reader who is interested to refer to the references to Scales and Modes in the Oxford Companion to Music, by Percy Scholes or to Grove’s Dictionary of Music and Musicians, and elsewhere. Scholes, for example, remarks of scales that “Apparently any combination of notes whatever may be adopted as the material from which a peasantry, or a composer, or a group of composers may make their tunes, and there exists not even one interval common to all the scales of the world”.
Traditional music of the Ga people
Authors: Nketia J.H.
Published: May 2016

It is easy for the visitor to Accra to imagine that the activities of bands like the Tempos Band, Blackbeats Band and Rhythm Aces are representative of the musical practice of the Ga people of Ghana today. Modern Ghana music, however, has not ousted the traditional musical types used in Ga area even though it has decreased their supporters by setting up a new community of taste. Traditional music and dancing associated with ceremonies of the life cycle worship, festivals and indeed with recreation are still practised in Ga villages and towns as well as in Accra by those for whom these activities still constitute part of their way of life. Much of this music is vocal music with or without instrumental accompaniment. The instrumental emphasis is invariably on drums and idiophones (gongs or bells, rattles, etc.,). Wind instruments—in the form of horns—are restricted to chiefs, or in a few instances to senior gods (e.g. Sakumo of Tema). There appears to be no survivals of traditional flute or stringed instruments. A summary of the characteristics of this music is given subsequently, beginning with the music of idiophones and drums.
Organisation of music in Adangme society
Authors: Nketia J.H.
Published: May 2016

The specialization which the requirements of social life bring into the content and organisation of folk music and dancing must engage the attention of the student of African music, for it is often by reference to this that the musical heritage of any given society can be discovered and evaluated. Investigation into the practice of music of the Akan, Ga, Adangme, Ewe and other peoples of Ghana shows that this specialization is widespread and tends to follow the pattern described subsequently for Adangme society. Traditional Adangme music is very limited in its music resources, more so than the music of their Ghanaian neighbours. Much of it is vocal. The songs may be sung to the accompaniment of idiophones (bells, rattles, stock clappers, etc.) or they may be combined with drums. The variety of drums of Adangme origin in common use is small; the most important of them are the drums of Klama, the most widely used musical type in Adangme area. Adangme music has in common with the music of other Ghanaians both a polymetric and polyrhythmic foundation. But it is distinct in its style of singing and in its melodic and harmonic usages.
African musical instruments in Kenya
Authors: Hyslop Graham H.
Published: May 2016

There are many African musical instruments scattered throughout Kenya. In some cases it appears that there will be nobody to carry on this tradition when the present exponent dies. This means that in a short time, some of the traditional instruments of this country will have been lost without trace. Because of this danger, traditional instrumentalists were invited to attend a Course at Jeanes School, the Colony’s main centre for Adult Education, in September, 1958, in order that a careful study of these instruments might be made.
More Kenya musical instruments
Authors: Hyslop Graham H.
Published: May 2016

In the last issue of this Journal there was an account of a traditional instrumentalists’ course conducted by Kenya’s Music and Drama Officer in September 1958. As a result of this course considerable information was gleaned about some of Kenya’s musical instruments, particularly those from the Lake Victoria province of the country. In October 1959, instrumentalists were again invited to take part in another research course and twenty one instrumentalists accepted the invitation, fifteen again from the Lake province and six others from Digo country in the coastal area in Kwale district, not far from Mombasa.
Recording tour of the Tswana tribe: Western Transvaal and Bechuanaland Protectorate, October - November, 1959
Authors: Tracey Hugh
Published: May 2016

Little or nothing has been written or recorded in the last 25 years on the subject of Tswana music, and when the Field Recording Unit cf the Library set out to try to fill part of this gap, careful preparations were made beforehand. On account of the relatively short distances from the Library Headquarters which were involved and from well founded suspicions that the Tswana were not inclined to be co-operative, it was decided to make a preliminary tour in order to visit most of the Chiefs and villages where we intended to record.
Basutoland recording tour, November 19th to December 3rd, 1959
Authors: Tracey Hugh
Published: May 2016

For the short period in which the recording unit is active in the country of the tribes concerned we live intensely in the atmosphere of local society, ruler and ruled, teacher and taught, each with their special contemporary problems, the more so because the nature of our research gives us a background of similar conditions from other regions where we have been to collect music. Basutoland was no exception, although in view of the forthcoming constitutional changes it was not surprising to find that local conversation was pre-occupied with the political situation rather than the cultural. These foreground matters, however, must not obscure the background out of which they have arisen. The visitor to Basutoland, suitably forearmed with Hugh Ashton’s classic work on the Sotho, is immediately impressed with the rugged nature of the country, its great ranges of mountains which sharply divide the land into isolated districts, the lack of highways which make the interior almost inaccessible and familiar only to those on horseback, and the distinctive appearance of the Sotho people themselves whose customs in many respects reflect their environment. The silhouette of the blanket-swathed rider on his narrow, tripling cob with his conical grass-woven hat, is the hieroglyph which spells ‘Basutoland’ to the tourist.
Performance of Sampling/Resampling-based Particle Filters Applied to Non-Linear Problems
Authors: Ly-Tu Nga , Le-Tien Thuong , Tran-Hoang-Thi Oanh , Huynh-Kha Tu , Mai Linh
Published: May 2016

In this work, we propose a wireless body area sensor network (WBASN) to monitor patient position. Localization and tracking are enhanced by improving the effect of the received signal strength (RSS) variation. First, we propose a modified particle filter (PF) that adjusts resampling parameters for the Kullback-Leibler distance (KLD)-resampling algorithm to ameliorate the effect of RSS variation by generating a sample set near the high-likelihood region. The key issue of this method is to use a resampling parameter lower bound for reducing both the root mean square error (RMSE) and the mean number of particles used. To determine this lower bound, an optimal algorithm is proposed based on the maximum RMSE between the proposed algorithm and the KLD-resampling algorithm or based on the maximum mean number of particles used of these algorithms. Finally, PFs based on KLD-sampling and KLD-resampling are proposed to minimize the efficient number of particles and to reduce the estimation error compared to traditional algorithms.