bluuebunny/crossref_metadata_2025_split huggingface dataset:
Drilling Evolution in Changning Shale Gas Block of Central China
Authors: Chen Z. Y. , Moh T. C. , Phan V. C. , Li W. , Liu D. , Wang R. G. , Lim J. M. , Li W. J. , Huang B. 
Published: October 2015

Abstract
Changning shale gas block is located in the southern part of the Sichuan basin. It is one of the first pilot experimental shale gas blocks in China. The paper will elaborate the drilling challenges in the field and the overall drilling performance with conventional approaches. In 2014, new drilling tools and methods were tried and applied. These significantly improved the performance, further elevating the drilling speed to a new level.
The paper will review the drilling performance of horizontal wells completed previously in the field. It will focus on demonstrating formation characteristics, well trajectory and geometry design, drill bit and directional bottomhole assembly (BHA). One of the biggest challenges is the hard rock on top of the shale formation that constrains the drilling speed, especially when designing the curve interval at the hard rock. By analyzing the drilling challenges, a new drilling system and method were introduced to the project in 2014 to combat the challenges. It has been proven successfully with actual drilling data.
Initially, as a pilot project, conventional motor technology was applied to six horizontal wells in Changning block. The average well drilling cycle was approximately 66 days for 1000 m of lateral section. The main challenge with motor drilling was high drag at the curve and lateral due to extreme friction as high mud weight was applied to balance the formation stability. This resulted in a poor on- bottom penetration rate during sliding mode. Directional work at the hard rock formation posed an additional challenge. In early 2014, a hybrid high-build-rate rotary system was applied to deepen the kickoff point and avoid the steering work in the hard zone. Air drilling was used to drill vertically across the hard rock. A power rotary steering system was also implemented to further improve the drilling speed in the lateral section. The combination of technical approaches led to significant drilling improvement. The rate of penetration (ROP) on bottom at the curve section has improved 200% over conventional drilling. The well drilling cycle was cut in half, which was considered as a breakthrough achievement in the field.
With the application of hybrid high-build-rate rotary steering system, the new well design can be executed. Air drilling is chosen to drill through the hard rock in the shortest distance. Using the power rotary steering system for the lateral further promotes the drilling performance to a new level.
Development of Reduced Order Modelling Techniques for Downhole Logging Sensor Design
Authors: Zhang Qiong , Mendez Freddy , Longo John , Gade Sandeep , Peyaud Jean 
Published: October 2015

Abstract
Spectral gamma ray tools provide insights into the mineral composition of formations and such data can be used to distinguish important features of the formation around the wellbore. However, it is a challenge in cased-hole cases to anticipate the attenuation effects of casing within various conditions of density and thickness in an efficient manner. In this work, an innovative reduced- order Monte Carlo modelling technique is presented for cased-hole environment spectrum analysis and, specifically, to numerically determine the attenuation effects of gamma ray transmission through different materials. The presented computational method is developed accounting for different casing and cement thicknesses, and sensor positions within the borehole.
The reduced order model construction could be considered one level up from the regular Monte Carlo modelling procedure as it reduces the dimensionality induced by various parameters and therefore proves an extremely useful tool handling large-scale problems that are very common in complicated downhole environment. The adjusted source distributions are then utilized to generate and validate spectra to be applied for difference logging scenarios. Two exemplary field cases are presented: 1. An open-hole logged well; 2. The same set-up well but with steel casing.
The reduced modelling techniques are applied to the both cases and the possible impacts of different variable. e.g. borehole size, mud weight and cement thickness on the sensor-obtained spectra are discussed. Future work will involve a series of case studies .e.g. the sensitivity assessment of formation impurities and an extension of the Monte Carlo computed elemental standards to a great variety of nuclear downhole sensor designs.
Identification of Borehole Breakout Formation and Estimation of Stress Direction and Regime Using LWD Ultrasonic Caliper Measurements: A Unique, Systematic, and Real-Time Methodology
Authors: Khoo C. Y. , Gland N. F. , Lee S. S. , Ng H.. , Wong F. K. , Za'ba M. A. 
Published: October 2015

Abstract
Wellbore instability remains a leading threat to oil operators as one of the main causes of non-productive time worldwide. As drilling technology advances, logging-while-drilling (LWD) measurements contribute valuable information to help identify instability problems in real time. One of the important measurements is the LWD ultrasonic caliper measurement, which makes it possible to identify borehole washout, breakout, keyseating, and spiral-hole conditions. Having this measurement enables diagnosis of wellbore stability problems while drilling without the need for an additional logging run, which is especially critical in an unstable wellbore.
In the industry, breakout identification using image data can be a significantly user-dependent process and requires appropriate skills. The process is time consuming, and the final result can still be subjective. Further complication comes when considering a highly deviated well path or when the field stress regime is abnormal. As a consequence, drillers face difficulties using the LWD ultrasonic caliper data directly for wellbore stability diagnosis. We propose a methodology to overcome the limitation of conventional method and produce reliable quantitative breakout data to be used in real time, in an automated, systematic, and consistent way.
An engineering-based workflow is introduced to distinguish zones of stress-induced breakouts from other borehole enlargement types with improved consistency and which can be easily translated into programming language. Instead of image data, this solution uses sector data to extract the borehole shape information using the cubic spline method. Six stringent LWD ultrasonic caliper-specific breakout criteria are introduced and used to identify breakout intervals from the borehole shape data.
Adopting the idea from the World Stress Map (WSM) project, a data quality ranking was also performed using the result of the workflow. The quality ranking criteria (defined by WSM project) segregate the breakout results into five categories to infer the reliability of the breakout intervals identified. This quality ranking procedure will greatly improve the reliability of the output data in the workflow prior to quantitative usage. The result of the breakout identification is then used to determine the principle stress direction and the stress regime, using a 3D stress analysis method for deviated wells.
An Improved Approach to Simulate Low-permeability Fractured Reservoirs with Dynamic Hybrid Dual-Porosity Model
Authors: Shuhong Wu , Tianyi Fan , Xiaozhou Zhang , Hua Li , Qiaoyun Li , Xiaobo Li , Baohua Wang 
Published: October 2015

Abstract
It is a challenging work to simulate fractured reservoir from reservoir description stand point, especially low-permeability reservoir with natural/artificial and water-injection-induced fractures. This type of reservoir has been idealized by a set of disconnected matrix blocks within a network of connected fractures such as Dual Porosity model. It is assumed that fracture network is primary continuum for fluid flow, the matrix of low permeability, high storativity is considered to be a sink/source to the fracture. The matrix and the fracture communicate through an exchange term which describes fluid flow between matrix and fracture. It is assumed that the fracture system is in a steady state which does not change during production history.
In the development process of low-permeability reservoir with fractures, some phenomena arose different from the above assumptions. Water injection with high injection pressure will induce new fractures. The distribution of natural/artificial fractures will be complicated. The fractures would be open, get bigger in width/length or closed during the production with the variation of reservoir pressure. The above type of fractured systems could usually experience some abnormal phenomena such as high injection pressure in injectors but low pressure in producers at early stage while serious water channeling and high watercut at the medium stage of development. It is difficult to explain these phenomena by existing principles.
A dynamic hybrid dual-porosity model is presented for the serious water-channeling phenomena in the fractured low-permeability reservoirs in which dynamic fracture model and psudo-tenser permeability model are overlapped to Dual Porosity model. The fracture network is considered to be in unsteady state in which fracture has possibility to widen, lengthen, close during oil production. A K-tensor is introduced to describe these processes, which is a function of pressure, stress, density of fractures. The paper will detail dynamic hybrid model such as its assumptions, equations, mechanisms and also its applications in low-permeability fractured reservoirs simulation such as in Changqing and Jilin Oilfield.
Challenges in Modeling of High Clay Volume Gas Reservoir with No Water Production
Authors: Ezabadi Mehdi Ghane , Ramli Anis Salwa , Ataei Abdolrahim , Othman Tg Rasidi 
Published: October 2015

Abstract
The characterization of high clay volume reservoirs is a challenge in terms of cut-offs determination, saturation modeling, and simulation setup. These can be even more complicated when it incorporates zero water production from the transition zone. In transition zone, both hydrocarbon and water are expected to move. However, dry hydrocarbon production from transition zone is a common phenomenon observed in many parts of the world. Modular Formation Dynamic Tester (MDT) and Drill Stem Test (DST) in three (3) appraisal wells in a high clay volume sandstone reservoir show no evidence of water production in spite of the long perforation interval just above the contact. This could be explained by different reasons depending on the type of reservoir lithology and mineralogy. One of the common reasons in sandstone reservoirs including this case is the presence of Smectite clay mineral in shale, which can immobilize large amount of water.
There are many challenges in characterization and modeling of this high clay volume, dry producing gas reservoir. For instance, how to estimate the amount of mobile and immobile water saturation in the transition zone, how to incorporate the capillary pressure (Pc) data in simulation while still maintaining the production performance, and whether or not the potential reserve and flow characteristics can be captured if petrophysical cut-off applied into the model. This paper will illustrate the case study in characterizing and building the dynamic model with immobile water in transition zone whereas the mentioned challenges are addressed. A novel method is presented to construct the model to estimate the total immobile water saturation using core and log data, and different approaches to initialize the model while evaluating the impact of Pc on reservoir performance are also further discussed.
A Case Study: Validation of Real Time Non-Isothermal Hydraulic Model Using Deepwater Managed Pressure Drilling Data
Authors: Hidayat Andri M. , Irawan Fikri , Karnugroho Ardia 
Published: October 2015

Abstract
Drilling through narrow window between pore and fracture pressure using Managed Pressure Drilling (MPD) approach requires precise hydraulic designs and pressure control plans to achieve drilling to target depth safely in timely manner which require accurate hydraulic model on pressure changes behavior along the borehole.
This paper presents a case study where a non-isothermal hydraulic model was validated using field data from successful Deepwater MPD well in Offshore East Kalimantan, Indonesia. The validation considers all relevant hydraulic parameters such as bottom-hole pressure, equivalent circulating density, circulating friction and surface back pressure. The hydraulic modelling validation results are important in order to determine the non-isothermal hydraulic simulator behavior against actual field data for continuous improvement for future MPD operation.
The validation confirmed the previous theoretical estimations that mud density and annular friction considerably depend on dynamic annular temperature profile. The work revealed that using a field-proof non-isothermal hydraulic model plays critical role in order to gather accurate BHP control in MPD operations.
During the MPD operations, employing real-time hydraulic model validated by PWD data will improve the dynamic pressure control during the operation, the accuracy, and reliability of the hydraulic simulation results. Hence, enhancing the MPD capability to assist drilling a well to zone of interest more safely and efficient.
Application of Bionic Metal Foam with Water Control Technologyfor Sand Control Screen
Authors: Jin Xu , Ding Bin , Chang Liling , Li Jianming , Bi Lina , Liu Yu'e , Long Ying 
Published: October 2015

Abstract
After billions of years of evolution, creatures in nature exhibit almost perfect structures and functions. Through learning from the nature, human beings are now able to develop biological multifunctional materials which can be applied to the engineering fields[1-5]. This paper focuses on foamed Nickel with bird-bone structures, which has advantages such as low density, high strength, controllable porosity, strong sand-containing capacity, and oil/water separation ability, etc. Previously, we have applied bionic Nickelfoam to down-hole sand control[6]. The open pore substrate has a very permeable structure, the porosity and the pore size of the metal foam can be varied in a large range to meet the sand control demand. The open pore Nickel foam is wrapped around a cylindrical geometry perforated base pipe. Sand bodies would settle inside the foamed metal after entering into pores without blocking thanks to the 3D characteristics of the porous structure. The number of foam layers and the pore sizes can be varied in order to achieve optimum flexibility for different sand control applications. Recently, in order to separate oil and water, the Nickel foam has been modified chemically. This paper demonstrates its superior properties in terms of special wettability, buoyancy, and corrosion repellency. Furthermore, high separation efficiency and long-term repeatability of oil/water separation can be reached according to a series of tests.
Characterization of Pore Structure in Tight Oil Reservoir Rock
Authors: Zhenpeng Leng , Weifeng Lv , Desheng Ma , Qingjie Liu , Ninghong Jia , Tong Li , Xu Jin , Danyong Li 
Published: October 2015

Abstract
The concern of global energy shortage forces people to divert their attention from conventional oil and gas resources to unconventional ones such as tight oil, shale gas, basin-centered gas, coal bed methane and gas hydrate. Tight oil, in consideration of technical feasibility and economical affordability, is regarded as one of the most promising unconventional resources. And it is necessary to make the characterization of realistic pore structure for tight oil, which is the foundation for continuous production and enhanced recovery. In this paper a novel analysis procedure to characterize the pore structure of the tight oil sample in three scales, millimeter, micrometer and nanometer, is proposed and performed on two core samples of tight oil reservoir from Chuanzhong Oilfield. Macro-CT is used to scan a whole core and to obtain millimeter scale images which represent the porosity distribution and the connectivity on the reservoir scale. Micro-CT and Nano-CT are used for identifying micropores and nanopores respectively, and the quantity and the connectivity of pores and throats are obtained by reconstruction for the pore scale network. Nevertheless, paradoxical issues of Micro-CT and Nano-CT scanning are the lack characterizations for pore size, pore type and pore origin. These issues can be resolved with the aid of SEM which generates a 2D image of the surface of the core sample covering the range of scales from nanometer to millimeter. In the millimeter scale level, the distribution frequency of porosity under 0.5% is about 40% which forms the main porosity area for both two core samples. In the micrometer and nanometer scale levels, pore scale networks show little connectivity for the matrix pore. Analyzing SEM images, it indicates that intergranular pore is identified with the diameter from 1 micrometer to 6 micrometer in the micrometer scale level and intragranular pore is identified with the diameter from 300 nanometer to 800 nanometer in the nanometer scale level. The microfracture system, which contributes to improve the effective permeability for tight oil, can also be well observed in SEM images with average length from 10 micrometer to 100 micrometer and averaged width from 1 micrometer to 3 micrometer.
Enhancing Coal Bed Methane Recovery by Varying-Composition Gas Injection
Authors: Sayyafzadeh Mohammad , Keshavarz Alireza , Alias Abdul Rahman , Dong Ky Anh , Manser Martin 
Published: October 2015

Abstract
Gas injection in coalbed methane (CBM) resources is a well-studied method. Findings indicate that although Carbon-Dioxide (CO2) injection expedites the Methane desorption process, its high adsorption affinity causes irretrievable permeability reduction. Nitrogen (N2) injection does not have the swelling issue, however, an early breakthrough of the injected gas occurs. Recently, through several simulation-based and experimental studies, it has been shown that a better result is obtained, when a mixture of CO2 and N2 is injected. In these studies, an optimum composition for the injected gas was found, by carrying out a series of sensitivity analyses for the given CBM with known geomechanical and sorption characteristics. In all of these studies, the composition of the injected mixture remains constant within the period of injection.
In the current work, in order to obtain a better performance, an alternative method is proposed in which the composition of the injected gas is adaptively updated during the injection through several steps. This method can postpone the breakthrough time and also keep well injectivity high. To evaluate the proposed method and find an optimal and practical injection schedule, a semi-synthetic model is constructed. Different injection scenarios are compared with each other, using a compositional simulator (ECLIPSE-300), which uses the extended Langmuir isotherm and the modified Palmer-Mansoori model. The compositional simulation allows us to investigate the sorption competition between each component through the whole system. By a series of sensitivity analyses, an optimum scenario is found. The best obtained scenario, is the one that begins by injecting a mixture with less CO2, and continues by a sequential rise in the CO2 fraction. The outcomes confirm that the proposed method has the following benefits, in comparison with the continuous injection: 1- higher Methane recovery, 2- deferment in permeability reduction, 3- later N2 breakthrough.
How Interpreting Log Data can Improve the Accuracy of Resource Assessment for Shale Plays
Authors: Wong Joanna , Bahar Mohammad 
Published: October 2015

Abstract
The recent developments of shale gas in the US have greatly encouraged exploration for the shale gas resource in Western Australia. The Merlinleigh Sub-basin of the Southern Carnarvon Basin in Western Australia has been found to contain high quality gas-prone source rocks from existing geochemical data. This paper demonstrates how log data can be used in the absence of geochemical data to increase the accuracy of resource assessments. An assessment of the Merlinleigh Sub-basin was used to calibrate and test the reliability and accuracy of the log method.
A major parameter for resource estimation is the thickness of a source rock layer. This is usually determined by geochemical analysis and identifying high TOC intervals from cores. Undeveloped shale gas basins however, are limited in geochemical data whereas most of the drilled wells have wireline log data. Passey's (et al. 1990) ΔlogR method encompasses a multitude of algorithms that predicts TOC from well logs and precisely determines the thickness of a layer. The method is first calibrated with known TOC from cores before applying to wells without geochemical data. Prior studies identified three formation layers in the Merlinleigh Sub-basin; Byro Group, Wooramel Group and Gneudna Formation; potentially containing high quality source rocks. After applying Passey's delta log R method to determine thicknesses, each layer was ranked according to rock characterisation factors such as TOC, generation potential, vitrinite reflectance, porosity and permeability. The Monte Carlo method by Crystal Ball software was then selected to estimate the probabilistic resources of all layers. The production ability of each formation can also be estimated using standard open-hole log data for estimating the Ultimate Recovery in shale gas resources.
In comparison, the TOC calculated from Passey's method produced results consistent with the known geochemical data, thereby validating both sets of data. The Wooramel Group was identified to contain the best quality source rocks, followed by the Byro Group, and lastly, the Gneudna Formation. According to P50 estimations from Crystal Ball, the Byro Group, Wooramel Group and Gneudna Formation contained resources of 51.6tcf, 40.7tcf and 1.4tcf respectively. The Ultimate Recovery for the above was found to be 4.69tcf, 3.71tcf and 0.13tcf respectively. Due to the low estimations for the Gneudna Formation, this paper will focus on the Byro and Wooramel Groups.
This paper explores a unique way of using Passey's method for undeveloped resources having limited log data but no geochemical data. The log data was also used to estimate the Ultimate Recovery based on the production ability of each well. The exploration potential of the Carnarvon Basin in Western Australia for unconventional gas has been identified and is the first geochemical assessment for the Merlinleigh Sub-basin.