bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unique Data Standardization Challenges and Solutions: Raw and Basic Processed Microseismic Data
Authors: Al-Thani Lulwah , Al-Naim Rand , Al-Zayer Ali , Bin Mahfoodh Abdulelah 
Published: April 2019

Abstract
Microseismic monitoring of multi-stage hydraulic fracturing has emerged as a key technology for unconventional stimulation wells to show the 3D propagation of the induced fractures. Monitoring the dynamic growth of these fractures gives insight into the quality of the completion design as well as better understanding of reservoir characteristics and rock properties.
The lack of industry standard format for microseismic data resulted in major challenges on different aspects of transmission, interpretation and archiving. This has raised the need to establish a standard format for both raw and basic processed microseismic data.
Basic processed data for each microseismic event is processed remotely in the field and transmitted in near real-time to central offices to be mapped and integrated with other data types using specialized technologies to enable timely decision making. Data should contain the minimum and sufficient information to characterize and indicate the location and magnitude of the induced fractures.
Raw microseismic files are large in size and typically delivered to data proponent in external storage devices at the end of the hydraulic fracturing operation. These files should contain additional attributes collected at the field for all microseismic events and stages such as trace header description, geophone orientation and specification. Both basic processed and raw microseismic data must be captured in a standard format to be stored in a corporate database to safeguard company assets, ensure data integrity and availability for future operations.
Data standardization for both basic processed and raw microseismic was developed by compiling the minimum data requirements from subject matter experts. The new standard for basic processed data consists of a vendor-neutral format that is suitable for all service companies and compatible with major interpretation and visualization technologies. This standard mainly focuses on setting guidelines for microseismic events location and magnitude. Raw microseismic files are in "SEGY" format that include additional meta data attributes such as frac stage number, treatment and monitoring well.
Solutions used to address current microseismic data exchange challenges went beyond data standardization to include modification of existing real-time data transmission system, interpretation technologies and database schema to accommodate and visualize microseismic data at different stages.
Future challenges of microseismic will include the need for technology and data transformation to adopt new generation processing technologies and algorithms to enable on-site data analytics and huge data transmission. This new approach will automate filtering signal from noise to streamline real-time signal transmission and ensure integrity. This session will focus on highlighting microseismic current and future data challenges including discussions on some of the proposed solutions.
Integrated Multiple Parameters Method for Candidate Selection in Refracturing Treatment
Authors: Lu Mingjing , Su Yuliang , Wang Wendong , Zhang Ge 
Published: April 2019

Abstract
Refracturing treatment are performed since stimulation effect won't last for entire life. Screening wells for refracturing needs a systematic analysis of huge amounts of data. With literature review, it is obviously that there are many factors controlling the success of refracturing and factors may vary in different oilfields. Proper factors and data processing are the primary principle in candidate selection. The Integrated Multiple Parameters (IMP) method is presented to provide assists in selecting candidate wells.
After deeply researching over 200 restimulated wells, all factors thought to be related with success of refracturing are listed and analyzed, results show that single factor may have great influence on restimulation but no significant patterns can be obtained since too many factors making things complicated. The IMP method proposes five parameters which are all integrated by those single factors. It is emphasized that all parameters have physical or engineering meanings which makes it easier to quantify their correlation in refracturing. Besides, all the parameters are dimensionless which makes it easier for using in mathematical models and statistical analysis.
The five dimensionless parameters are developed considering the most important aspects of candidate wells selection which are showed as followed: fracture reorientation, well completion, reservoir depletion, production decline, oil-water well connectivity. Parameters are calculated for all the restimulated wells to dig into their correlation with the outcomes of refracturing. A simple decision model is built to help with screening wells for refracturing. Results shows that it is more executable to evaluate and predict the success of refracturing with these dimensionless parameters. Fracture reorientation parameter is the primary one to be considered since it leads to fracture reorientation which brings significant production increment. Then two types of potential wells are picked: (a) wells with dissatisfied initial well completion, low production decline rate and high oil-water connectivity parameter; (b) wells with satisfied initial well completion, high well completion parameter, low production decline parameter, reservoir depletion parameter and low oil-water connectivity parameter for wells that are not easy for fracture reorientation. Wells selected are proved to be refracturing potential which verify the reliability and accuracy of IMP method.
The IMP method is an improved approach integrating most of the important factors which makes candidate selection much more predictable and it succeeds in screening out more than 80% of the potential wells in field test. Also, it can be applied widely in different oilfields since all the parameters are dimensionless. By combining with some mathematical methods such as neural networks, it can even predict increment of the restimulation treatment.
An Integrated Modelling Workflow to Optimise Initial Production Rate and Well Spacing for Longmaxi Shale Gas Play
Authors: Yong Rui , Zhuang Xiangqi , Wu Jianfa , Wen Heng , Shi Xuewen 
Published: April 2019

Abstract
Ning201 Longmaxi shale gas play is located on the southwest edge of Sichuan Basin. Block Ning201 surface is very mountainous and elevation range of drilling pads is between 400 meters and 1300 meters. The target layer of shale gas exploration and development is mainly the Wufeng Formation of the Ordovician system and the organic-rich shale interval of the Lower Longxixi Formation of the Silurian system. The total thickness is between 30m and 50m, and the overall buried depth is 2300~3200m. Field development of Ning201 shale gas play was geared up in 2014. During early appraisal phase before 2014, average testing results of wells were 10~15×104 m3/d. 7 vertical appraisal wells and 50 horizontal wells have been drilled and 38 horizontal wells among them have been put into production to evaluate optimized development strategy until middle of 2017. Changning area accomplished the construction of 15×108 m3/a production capacity. During production appraisal phase, different well spacing pads were configured, and some cross-well interference testing were performed to determine optimal spacing in Ning201 block. Only qualitatively understanding can be achieved with spontaneous field efforts and quantitative evaluation of long-term impacts on production with varying initial rate control and well spacing is still missing.
In this paper, an integrated modeling workflow was introduced to accurately simulate the production behavior of a representative shale gas well and to control production through a calibration model to optimize well spacing and maximize economic returns. The workflow begins with microseismic monitoring during shale gas well fracturing operations. Considering the fracturing pumping procedure, fluid and proppant volume and subsurface features, including formation, natural fractures and in-situ stresses, the heterogeneity of the hydraulic fracturing system propagation ensures that the simulated complex hydraulic fracturing network is in line with reality. After establishing a detailed hydraulic fracturing model, production performance is matched to history to better calibrate the conductivity of hydraulic fracture network in dynamic model as a relaible predicting tool.
Compositional Variation of Natural Gas in Kerogen During Production
Authors: Pang Wei , Akkutlu I. Yucel , Ding Shidong , Zhang Tongyi , Xia Wenwu 
Published: April 2019

AbstractOrganic matter in source rocks such as coal and shale hold significant amount of adsorbed gas. Laboratory methos are available to measure the gas amount stored in the source rock samples. However, adsorbed gas release from the organic pore network and its production using wells is an issue under debate. The intricacy in the debate is mainly due to the physical properties of the adsorbed phase adsorbed phase. The adsorbed phase has an unknown composition and its molecules released in a selective fashion controlled by the organic pore walls. The organic matter nanopores bring in added complexity to the analysis due to nano-confinement effects. Our objective in this study is to predict the gas composition in kerogen pores in order to gain insight into the compositional variation with the pore size distribution in the formation. This prediction should be done properly at the initial conditions and during the pressure depletion. Thus, we also would like to investigate gas desorption impact on the adsorbed hase composition due to production.A molecular simulation method is developed using grand canonicalMonte Carlo simulation to study the in-situ composition of natural gas in model matter pores. We used the composition of produced fluid from a Chinese shale gas well. In essence, the method redistributes the fluid composition back into the organic pores at initial reservoir conditions. Then one-by-one the pores are depleted while the compositional variation in the pores is monitored. The recovery is measured by comparing the residual hydrocarbon molecules at different pressure steps during the depletion. The mean free path length of the fluid molecules, the fluid density and viscosity are computed once the thermodynamic simulation reaches an equilibrium.
Geomechanical Anisotropic Method Increased Fracturing Efficiency in Tight Oil Production: A Case Study of Yanchang Formation, Ordos Basin
Authors: Xi Shengli , Hou Yuting , Li Xianwen , Hu Xifeng , Liu Peng , Zhao Xianran 
Published: April 2019

Abstract
The Triassic Yanchang formation is rich in tight oil resource at Ordos Basin. The oil sandstone and oil shale of Chang 7 member are widely spread in the basin and have huge potential in oil production. Due to low porosity and low permeability, producing oil from tight oil reservoir depends on hydraulic fracturing. A successful hydraulic fracture requires accurate estimations of horizontal stresses and rock elastic properties in design and operation.
Chang 7-2 is shale and sandstone interbed reservoir and Chang 7-3 is shale oil reservoir with lamination sedimentary structure. The rocks with lamination structure are very anisotropic, and it needs to be considered in computation of horizontal stresses and rock elastic properties.
In this paper, we present a case study to illustrate the advantages of anisotropic geomechanics model. Anisotropic horizontal stresses and rock elastic properties were calculated and used in hydraulic fracturing design. The perforation intervals were selected at depths with low stress magnitude based on stress profile. The perforations efficiency was analyzed, and perforation interval with low efficiency was removed. Major stimulation operation parameters, total volume, proppant volume and slurry rate, were optimized with anisotropic geomechanics model. Fracturing operation results showed that the total volume was decreased by 16.5%, proppant pumped increased by 11.4% and daily oil production increased by 73.7%. This case study demonstrated that anisotropic geomechanics model help to improve operation efficiency and increase oil production.
Modeling and Experiments for CO2 Blowdown from the Cryogenic Pilot Plant and the Mitigations Measure
Authors: Surmi Amiza 
Published: April 2019

A pilot of cryogenic distillation technology is designed and installed for separation of the high CO2 concentration of feed up to 80 mol % from natural gas. However, the main concern was the dry ice formation during depressurization or blowdown might cause the pipeline and equipment blockage and consequently resulting in safety issues.
A dynamics simulation and modeling were conducted using commercialize software to determine the settle out temperature during the blowdown especially emergency condition. The investigations were focused on the high operating pressure and low operating temperature with a high CO2 composition which is closer to transient condition and solid region. Then, more comprehensive modeling was conducted by incorporating the equipment and piping design data including the sizing of relieve valves (RVs) and blowdown valves (BDVs). The accuracy of information is very crucial to obtain more reliable results.
It was observed that at high operating pressure, (50 to 75 barg) and low operating temperature,(-58 to 15 °C) the settle out temperature due Joule-Thomson (JT) effect were −58 °C and −92 °C for 60% and 80% CO2 concentration, respectively. Based on the phase diagram, in this condition, the CO2 will be under a solid region. As a result, the Minimum Design Metal Temperature (MDMT) of −100 °C was selected for equipment and pipelines design to avoid material brittle-fracture. Few mitigations measure were designed and installed to avoid the CO2 solidification. The BDVs were installed at the warmer area to minimize the JT effect leading to lower operating temperature than CO2 solidification temperature resulting to potential equipment blockage. The electrical heat tracings were installed at the outlet flange and outlet line of RVs and BDVs to maintain fluid temperature above CO2 solidification limit. This is to prevent CO2 solid from attaching to the pipe wall and build up in the piping in the event of relief. Another mitigation was by installing the outlet line with sloped toward vent header and free from instrument probe or sensor to prevent CO2 solid from build up at piping dead leg section. As a result, no sign of CO2 solid found in the sections that equipped with mitigations measure during experiments.
An inherently safer design of equipment and pipelines are very crucial especially for high CO2 concentration, high operating pressure and low operating temperature with the appropriate mitigations to avoid catastrophic failure.
Evaluation of Dynamic Reserves in Ultra-Deep Naturally Fractured Tight Sandstone Gas Reservoirs
Authors: Luo Ruilan , Yu Jichen , Wan Yujin , Liu Xiaohua , Zhang Lin , Mei Qingyan , Zhao Yi , Chen Yingli 
Published: April 2019

Abstract
Ultra-deep naturally fractured tight sandstone gas reservoirs have the characteristics of tight matrix, natural fractures development, strong heterogeneity and complex gas-water relations. There is strong uncertainty of gas reserves estimation in the early stage for such reservoirs, which brings big challenge to the development design of gas fields. Taking Keshen gas field in Tarim basin as example, during the early development stage, the dynamic reserves were much less than those of proven geologic reserves. As results, the actual production performances are obviously different from those of conceptual design. What are the reasons? How to adjust the development program of gas field? Based on special core analysis, production performance analysis, gas reservoir engineering method, and numerical simulations, influencing factors on evaluation of dynamic reserves for ultra-deep fractured tight sanstone gas reservoirs are analyzed. The results show that rock pore compressibility, recovery percent of gas reserves, gas supply capacity of matrix rock, water invasion are the major factors affecting the evaluation of dynamic reserves. On the basis of above analysis, some suggestions are given for the evaluation of dynamic reserves in Ultra-deep fractured tight sandstone gas reservoirs. For this kind of reservoirs, it is reasonable to determine the gas production scale based on dynamic reserves instead of proven geological reserves.
A DNN Trained to Pick Faults in Seismic Data: Implementation and Results
Authors: Montaron Bernard , Montaron Francois , Montaron Renaud 
Published: April 2019

Abstract
A software system based on deep neural network (DNN) technology was designed and trained to recognize fault lines in 2D seismic vertical sections, and fault surfaces in 3D seismic cubes. The system was successfully tested on public domain data from several basins in New Zealand. The paper describes the key components of the system and explains how they were designed. A relatively small size window is used to scan 2D seismic sections. Two DNNs identify if the window contains a fault and output the vector corresponding to the fault segment in the window. After scanning the entire section, a clustering algorithm is applied to group these vectors in separate clusters corresponding to the faults in the section. Finally, a linear regression algorithm calculates the fault lines – not always straight – in the section. Fault lines in successive 2D vertical sections of a 3D cube are associated to form fault surfaces. The training data set that was created to train the DNNs contains 120,000 examples. The validation test set has 30,000 examples. A special workflow and software were developed to generate these 150,000 labelled examples with a mix of synthetic and real data. The results obtained are quite satisfactory: the success rate exceeds 95% on the validation test set. The vector clustering algorithm properly handles crossing faults. The system is designed to quickly learn to correct mistakes highlighted by geophysicists, like patterns wrongly identified as faults, or missed faults. This system was trained to identify fault patterns in seismic data just based on examples. The concept can easily be expanded to recognize many other types of patterns such as structural or stratigraphic traps, horizons, and types of seismic facies. This fault detection software is the first step toward a machine learning-based system for automated structural interpretation of seismic data.
Well Stimulation Evaluation in Horizontal Wells with Emphasis on Petrophysics and Rock Mechanics: A Case Study in Deep, Tight Carbonate Formation
Authors: Zhou Yuhai , Zhang Wenyu , Zhu Ding 
Published: April 2019

AbstractTight carbonate formations with extremely low porosity and permeability depend on well-designed completion and stimulation treatments to achieve economic production. Acid fracturing, a relative cost-effective choice compared with propped fracturing, is widely used for carbonate stimulation. However, many factors contribute to the acid etching created conductivity, which is a key parameter for the success of acid fracturing. From a petrophysical perspective, depth-by-depth rock mechanical properties, stress distribution as well as the heterogeneous petrophysical properties (e.g. porosity and permeability) are important local information affecting final fracture conductivity. In this paper, we conduct an integrated evaluation for multi-stage acid fracturing in a horizontal well in a deep, tight carbonate reservoir in Tarim field, China.We perform multi-mineral analysis and estimate volumetric concentrations of minerals, porosity, and fluid saturations with conventional well logs. Since shear wave sonic logs are not available for most of the wells, we estimate rock mechanical properties (Young's modulus and Poisson's ratio) using effective medium models including self-consistent approximation and differential effective medium theory. Corrections including the impact of fluids are developed using Gassmann's fluid substitution. Besides, we estimate depth by depth permeability with empirical correlations. Core measurements are used for cross-validating the well-log-based estimates of rock mechanical properties, porosity and permeability. Horizontal stress distribution and closure stress field are generated using poroelasticity stress model with estimated Young's modulus and Poisson's ratio as inputs. We also perform variogram analysis on well-log-based estimates of permeability and obtain its correlation length in both vertical and horizontal direction to quantify formation heterogeneity.The estimated rock mechanical properties, stress distribution, and petrophysical properties are used as inputs to 3D acid fracturing treatment modeling. The simulated fracture geometry, especially fracture height, is highly dependent on stress variation. The modeled acid transportation in fracture is strongly affected by permeability correlation lengths. The study result shows that the conductivity created by acid fracturing under local high closure stress is insufficient for successful acid stimulation treatments.
Environmental Impact Study and Experience Sharing of Produced Water Reinjection from Unconventional Gas Development
Authors: Chen Changzhao , Li Xingchun , Wu Baichun , Zhang Kunfeng , Song Quanwei 
Published: April 2019

Abstract
The world has seen a peak in unconventional gas development in recent years. Based on the practice of unconventional gas field development domestic in China and abroad, it is risky that the reinjection water may contaminate groundwater in local or adjacent areas during reinjected fluid migration. Ensuring environmental safety of the reinjection is a multi-disciplinary system project. This paper carries out the analysis and shares the experience of China's practice based on the actual cases from the following aspects. 1) The screening of the well location and the formation of the reinjection. 2) The drilling and cementing construction of the reinjection well, which considers the factors such as cementing quality and cement height and casing material. 3) The estimation of the total reinjection capacity, and the factors such as porosity and permeability of the geologic trap and reservoir fracture pressure is considered. 4) The monitoring of well and migration of reinjection fluids. Further environmental risk study of produced water reinjection is presented in this paper, on both sandstone formation of tight sand gas field and carbonate karst formation of shale gas field in China's typical unconventional gas development areas, using laboratory geochemistry experiments and large area geophysical test to obtain seismic data.