bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Pipe Rotation on Dynamic Well Control Surface Pressure Using Single Bubble Model
Authors: Al Marhoon Zahrah , Al Ramis Hussain
Published: April 2019

With the recent advances of drilling technology, carrying a safe well-constructed design is very important especially implementing the well control strategy. Managed Pressure Drilling (MPD) is a new technology that has recently emerged in the industry. It has special well control capabilities supported by the RCD to simultaneously provide the required pressure control on a certain volume gas influx and maintain the pipe rotation for drilling or any required operation. This paper examines the effect of pipe rotation on casing pressure profiles during the circulation process of the kick using MPD equipment.

Data from real scale kick experiments conducted by the LSU Petroleum Engineering Research & Technology Transfer Laboratory (PERTT Lab) personnel was analyzed. These experiments were conducted in a controlled environment that mimicked downhole conditions with a gas influx entering the wellbore. Then, the experimental analysis was coupled with the effect of pipe rotation through the application of correlations. The correlations from literature show a change in the expected frictional pressure loss when comparing the rotating case to the non-rotating case. The estimate in the change of frictional pressure loss in the annulus for non-Newtonian fluids with pipe rotation was done using two different correlations. This change is then applied on the geometric configuration of the well to find the change in the surface casing pressure caused by rotation.

This paper covers the use single bubble model in WBM. The model examined the change on the surface pressure caused by frictional pressure loss from pipe rotation.

The results from the models showed that the changes in pressure is very small with a percentage change up to 8 %. These changes are only applicable to cases with similar mud properties and well design of the experiments.

The practical outcome is to further the understanding of a gas bubble behavior in a wellbore experiencing a kick situation. Since new technologies allow for the rotation of the pipe during the circulation process, this paper helps in answering the question of whether or not the pipe rotation aids to overall expected surface pressure. Furthering the window of applicability of the MPD can possibly touch into its unexploited potential.
An Improved Model for Gas-Liquid Flow Pattern Prediction Based on Machine Learning
Authors: Mask Gene , Wu Xingru , Ling Kegang
Published: April 2019

Flow pattern of a multi-phase flow refers to the spatial distribution of the phase along transport conduit when liquid and gas flow simultaneously. The determination of flow patterns is a fundamental problem in two-phase flow analysis, and an accurate model for gas-liquid flow pattern prediction is critical for any multiphase flow characterization as the model is used in many applications in petroleum engineering. The objective of this study is to present a new model based on machine learning techniques and more than 8000 laboratory multi-phase flow tests.

The flow pattern is affected by fluid properties, in-situ flow rates of liquid and gas, and flow conduit geometry and mechanical properties. Laboratory data since 1950s have been collected and more than 8000 data points had been obtained. However, the actual flow conditions are significantly different with any laboratory settings. Therefore, several dimensionless variables are derived to characterize these data points first. Then machine learning techniques were applied on these dimensionless variables to develop the flow pattern prediction models. Applying hydraulic fundamentals and dimensional analysis, we developed dimensionless numbers to reduce number of freedom dimensions. These dimensionless variables are easy to use for upscaling and have physical meanings. We converted the collected data from actual laboratory measurement to the variations of these dimensionless variables. Machine learning techniques on the dimensionless variable significantly improved their predictive accuracy. Currently the best matching on these laboratory data was about 80% using the most recently developed semi-analytical models. Using machine learning techniques, we improved the matching quality to more than 90% on the experimental data.

This paper applies machine learning techniques on flow pattern prediction, which has tremendous practical usages and scientific merits. The developed model is better than current existing semi-analytical or classical correlations in matching the laboratory database.
Comprehensive Analysis of Caprock Failure and Associated Steam Release Events During SAGD Operations
Authors: Matsuno Shiho , Furui Kenji
Published: April 2019

Massive steam injection during SAGD operation may result in significant changes in pore pressure, temperature, stress and strain in the overlying caprock as well as the injected formations. These changes lead to containment breach of the caprock as reported in the steam release incident at the Joslyn Creek field in 2006. To avoid such a catastrophic event, the integrity of the caprock and risks of steam release must be properly evaluated during planning and operating SAGD wells.

In this study, a thermo-poro-mechanical model is developed to evaluate the integrity of the caprock due to temperature and pressure changes observed during SAGD operations. A commercial reservoir simulator is used to calculate changes of pore pressure and temperature during steam injection. These results are used as a part of input data for the geomechanical model that considers poro-elasto-plastic stress-strain relations of the formations. The shear failure of the rocks is determined by the Drucker-Prager criterion while the tensile failure is judged by the tensile strength of the rocks, which are used to assess the integrity of the caprock.

Our simulation results indicate that the temperature change can be extended deep into the overlying formations while the steam chamber is developed in the reservoir interval. Because the caprock is expected to have low permeability, these temperature changes lead to notable pore pressure changes in the caprock interval, which plays an important role in the stability of the caprock in the geomechancial analysis. The simulation results also suggest the importance of considering free surface, underburden, and sideburdens as well as assigning appropriate boundary conditions in the model.

Using the model developed in this work, the Joslyn field case is investigated showing the existence of failure region in the caprock layer during the steam circulation phase. These findings may explain the mechanism of the caprock failure and the resultant steam release at the surface experienced in the field. It should be noted that the analysis results indicate, not only possible shear failure events but also a possibility of tensile failure developed in the caprock interval above the steam chamber. It is also found that the geological complexity including the existence of a mudstone layer between the reservoir and the caprock affects the likelihood of the steam release event.

The caprock integrity analysis method presented in this work can help engineers evaluate risks of the containment breach during a planning phase of SAGD project. Also, using the simulation model developed in this work as a forward model, the integrity of the caprock and the development of steam chamber during SAGD operation can be monitored by surface displacement measurements by In-SAR or tiltmeters. These study results can enable effective and safe operation for future SAGD production.
Digitalization Using IIoT and Cloud Technology in Oil and Gas Upstream-Merits and Challenges
Authors: Dange Aarti , Ranjan Pallavi , Mesbah Hossam , Chokshi Rajan
Published: April 2019

This paper discusses the application of IIoT in various areas of oil and gas upstream. It elaborates on the drivers of IIoT, presents the advantages and benefits and describes the challenges faced as of today in the implementation. IIoT and cloud computing work hand in hand. IIoT generates huge amount of data and cloud computing provides a pathway to present this data is a useful way and travel to the end user. A detail evaluation of the investment in using this technology and its anticipated returns are demonstrated. IIoT is believed to be an emerging solution for oil and gas complexities. The main drivers behind this technology are data storage, data analytics, reliability improvement and materiality assessment and control. The application of IIoT in areas of artificial lift optimization, Supply chain in real time, cyclic steam stimulation and flow assurance is described. This technology provides real time solution for dynacards interpretation and analysis for Sucker rod pumps, operating point analysis for Electrical submersible pumps and predicted cumulative production for all artificial lift optimization; efficient planning and waste elimination for supply chain and logistics; real time steam quality and quantity check for CSS and a complete digital approach to reservoir management and flow assurance. The main benefits of this technology are reduced MTBF, high efficiency, improved HSE standards, Instantaneous control over production loss, collaborative decisions leading to fast turnaround, highly responsive supply chain and enhancing environmental footprint. This has helped substantially in real time management of wells by exception and alerts in form of intelligent alarms indicating any deviation in the expected behaviour. This has significantly brought down the non-productive time (NPT). However, this paradigm shift comes with a substantial cost. The technical challenges include the data security, protocol non-uniformity, possible data loss and limitations of redundant system.
Electrical Submersible Pump Material Compatibility for High TDS Application
Authors: Kalu-Ulu Torty , AlBori Mostafa
Published: April 2019

The selection of completion equipment for artificial lift string for any field in the oil and gas industry is important for the safe and reliable operations of such a field. This is critical to the management and overall profitability of the oil and gas asset, especially in areas where artificial lift is the predominant means of water injection and hydrocarbon production. This paper focuses on why it is important to understand the saline subsurface and the total dissolved solids (TDS) of the environment in which the artificial lift completion is to be deployed and its impact on equipment selection.

High concentration of corrosive components in the well fluid such as hydrogen sulfide, chlorine and total dissolved solids makes the well fluid conducive for electron migration. Such migration causes heavy corrosion, especially when dissimilar metals are used in artificial lift well completions. Carbon steel tubulars and casing are easily affected by such corrosive composition and leads to premature failure of artificial lift completions, which poses safety and operational issues. This type of environment is intense in electrical submersible pump completed wells because of the electromagnetic field generated by the current passing through the electrical cable of the pump system.

A combination of field and laboratory data gathering, and analysis was utilized to determine the effect of the aggressive components of the produced fluid on electrical submersible pumps assembly. The contributions of the high total dissolved solids in the conductivity of the well fluid, and in the electrochemical process for metal corrosion were analyzed. It was evident from both forms and approaches utilized in the analysis that well fluid becomes an electrolyte that provided the desired path for electron flow, which was enhanced by the magnetic field of the ESP system cable.

This paper highlights the integration of three approaches of geochemical analysis of well effluent, Anodic Index differential and tubular internal coating in corrosion prevention and electric submersible pump runlife elongation in wells with corrosive compositions including high total dissolved solids.
Real-Time Automated Drilling Optimization and Operations Benchmarking Services Deliver a Step Change in Khalda Western Desert Operations
Authors: Abdel Mageed Mohamed , Awad Mostafa , Hussein Ahmed , Osman Ahmed , Siam Mahmoud , Al-Kaabi Mohammed , Rafik Ahmed
Published: April 2019

Egypt's Western Desert is known to be a highly complex and difficult drilling environment. Drilling in this area suffers from multiple geological risks related to formation dip and hardness, faulting, interbedding, and abrasive lithology. These conditions have typically caused drilling problems and costly delays in wells delivery. Combined with the geological difficulties, differences in the implemented drilling practices and operational procedures have led to inefficiencies and the loss of some knowledge transfer among different drilling activities and field operations.

For a proof of concept in one of its fields, Khalda endorsed a drilling automation and operations benchmarking strategy to improve the well delivery time in one of its Western Desert fields. The strategy focused on on-bottom drilling activity as well as off-bottom practices and flat-time activities. One part of this strategy endorsed a real-time automated drilling optimization workflow for the on-bottom drilling activities whereby the implementation of a change-point algorithm dictates the optimum drilling parameters to obtain the best possible rate of penetration (ROP) within the rig and drilling assembly constraints and while operating within the safe drilling dynamics window for the assembly. This approach yields the optimum ROP and prevents any possible downhole equipment failure or premature bit damage. The other part of the strategy involved benchmarking the different rig activities while drilling or doing other mechanical operations to gauge the activity of the current well compared to the offset well. This highlights any inefficiencies that can be immediately overcome, areas of improvement, and key learnings for future optimization or implementation.

This strategy was implemented in a deep gas development well in a challenging Western Desert field with known problematic offsets. The results showed a step change in well delivery whereby the well finished 3 days ahead of plan and 7 days ahead of the offset well. The real-time automation technique for drilling optimization managed to show 24% on-bottom ROP improvement in one section, enabled completing another section with a one run less than offset, and managed to mitigate the harsh drilling dynamics to prevent downhole equipment incidents. Also, the activities benchmarking helped to develop standard drilling practices that reduced inefficiencies in off-bottom drilling activities by 50% and managed to highlight key learnings and areas of development for future wells. These results helped in validating the proof of concept set at the beginning of this pilot.
Hydraulic Fracture Calibration for Unconventional Reservoirs: A New Methodology for Predictive Modelling
Authors: Pankaj Piyush , Shukla Priyavrat , Wang Wei Kan
Published: April 2019

Hydraulic fracture calibration in an unconventional environment is a complex process and is inconsistently practiced. Automated calibration methods are not effective or efficient in accounting for the heterogeneity and variation of constraining parameters. However, it is important to build a consistent methodology to calibrate hydraulic fractures incorporating the observed data. This paper covers the systematic "Seismic to Simulation" workflow for unconventional reservoirs to constrain a hydraulic fracture model to obtain a calibrated result.

For the hydraulic fracture calibration, injection fall-off tests, sonic logs and image logs are commonly used as the primary inputs to calibrate the geomechanical model. A new workflow is developed to be used consistently incorporating the learnings from the traditional fracture calibration methods. Impact of high stress barriers and height and pinchouts of fractures are incorporated in a geomechanical-flow model. Simultaneous matching of the observed net pressure trend, incorporating the effect of reservoir laminations on fracture height growth is made using a complex fracture model. The effect of the natural fracture networks (NFN) on pressure losses and proppant transport is also accounted for in the fracture geometry. Further, hydraulic fracture geometry is calibrated using the microseismic data. The production behavior was validated using numerical simulation for production history matching.

A case study from the Permian basin is considered for the paper. The fracture geometry and footprint obtained using the calibration workflow match very closely the observed surface and downhole measurements. We constrained the model by matching the net pressures and achieved simulated production to match within 10% error compared to the actual oil and gas production. The fracture geometry was calibrated using microseismic data and controlled by incorporating the effect of weak interfaces and laminations. This workflow successfully demonstrates hydraulic fracture model calibration using pressure matching, microseismic data and production history matching. Systematically and consistently using this workflow provides solutions for infill well planning and well spacing for asset optimization.

This paper explains a systematic fracture calibration procedure that can be easily adopted by the operators to obtain reliable results in unconventional wells. The effect of reservoir laminations and impact of natural fracture in calibrating the fracture geometry and fracture pressure trend is uniquely demonstrated in this study.
A 3-D Hydraulic Fracture Propagation Model Applied for Multiple-Layered Formation
Authors: Tang Jizhou , Zuo Lihua , Xiao Lizhi , Wu Kan , Qian Bin , Yin Congbin , Ehlig-Economides Christine , You Xiangyu
Published: April 2019

Rock layering, a critical factor in determining fracture height growth, is pervasive in the Silurian Longmaxi shale formation in the southwest of China. From field studies, engineers found that the created fracture height is lower than the required height even after they enhanced the pumping rate to a very high value. This paper introduces a coupled three-dimensional hydraulic fracture propagation model considering the effect of bedding layers and investigate the effect of shear displacements along the bedding planes on fracture height growth. Our fracture propagation models address rock deformation and fluid flow. Rock deformation is governed by a fully three-dimensional displacement discontinuity method (3D DDM). The fluid flow model employs a finite difference method able to capture fluid movement along vertical fractures and bedding planes. Additionally, a propagation criteria determines whether the fracture would penetrate bedding planes. The Longmaxi shale formation has characteristics of large burial depth, low porosity and multiple bedding layers that hamper reaching the target fracture height even after increasing the pumping rate and treatment size. Hence, our fracture propagation model is applied to study the effect of bedding layers on fracture height growth. In this paper, we selected two different fracture geometries and analyzed profiles of fracture width, pressure and two types of shear displacement discontinuities. From numerical investigations, we found that the maximum width can be obtained at the junction after the vertical fracture penetrates the bedding planes as a result of the decrement of the compressive stress acting on the bedding planes. As the fracture penetrates the bedding planes, a certain amount of fluid would leak into the planes, which leads to fracture height containment. Moreover, the slope utilized for characterizing the correlation between leak-off volume and fracture height, is regarded as a tool to identify the number of BPs that fracture penetrates through. This paper illustrates the extensive application of our coupled hydraulic fracture propagation model for the Silurian Longmaxi shale formation with multiple bedding layers. Shear displacements along the bedding planes are regarded as a primary mechanism of fracture height containment.
Extended Acoustic Sand Monitoring Helps to Understand Ceramic Sand Screen Failure: A Case Study
Authors: Riyanto Latief , Sidek Sulaiman , Hugonet Vincent , Yusuf M Hafizi , Salleh Nurfarah Izwana , Ambrose Jonathan Luke
Published: April 2019

Many oil and gas fields have long been suffering from sand production due to either the absence or failure of primary well sand control. To avoid mobilizing costly work-over rig to pull out the tubing, operators have tried various thru-tubing remedial sand control. The well's condition such as sands accumulation and space constraints due to small inner diameter of tubing always make this remedial job challenging. It is not surprising that the results are not all satisfactory.

Among the industry-recognized remedial sand control, Stand Alone Screen (SAS) is the simplest and the cheapest method. Many SAS have been installed but most were failed with screen erosion as the main failure mechanism. Flowing high velocity fluid with sands wears out the screen fast making it impossible for the sands to bridge and to create formation sand pack around the screen.

Ceramic Sand Screen (CSS) technology which was recently introduced to the industry aims to address this erosion issue. Having more than ten times hardness of stainless steel, sintered silicon carbide ceramic material in CSS offers superior resistance to wear. The pilot was conducted by installing CSS in three (3) selected wells with sand production history. While waiting for acoustic sand monitoring installation, the wells were put on production with the same choke size and regular manual samplings were conducted to monitor the sand production.

The acoustic sand monitoring campaign began in November 2017. Sands production was carefully monitored during the process to determine the final choke size at which the wells would continuously produce. In the middle of the campaign due to adverse weather conditions, all non-essential personnel had to be abruptly demobilised from the field leaving acoustic sensors hooked-up to the respective flow line. This gave opportunity to have unplanned extended sand monitoring window.

Loss of Primary Containment (LOPCs) occurred in two CSS wells not long after that. In one the choke body was heavily eroded and the other well had a punched hole at the first elbow of the flowline. These incidents prompted full investigation to be conducted. This included pulling out the installed CSS and performed tear down analysis. Acoustic sand monitoring that just happened to be available in one of the wells proved to be critical in understanding the CSS failure.

The paper presents briefly on the CSS pilot project, the chronology of events until the incident, sands production trend from the acoustic sand monitoring. Using all available information, the paper provides details analysis on CSS failure mechanism.
Tight Coupling of a Reservoir Simulator With a Transient Flow Well Model: A Field Case Application to Optimise Cyclic Production in Liquid Loading Regime for a Tight Gas Field
Authors: Rasoanaivo Ombana , Danquigny Jacques , Henry Pierre , Hopkinson David , Liu Adeline , Marty Jacques , Marmier Rémy
Published: April 2019

Using a software integrator, a commercial reservoir simulator is tightly coupled with a commercial Transient Well Model. This is required when transient reservoir behaviour interacts with transient wellbore phenomena. It is the case in a tight gas field which is being developed since 2012 in China; long natural cycles of gas production in liquid loading regime followed by period of low or quasi nil-gas production are observed. Cyclic production is also being implemented to optimize the average gas production. In both cases, usual decline curve analysis is no longer valid. And computing long term production forecast becomes a challenge. The innovative application presented in this paper is an optimization of Cyclic Production in Liquid Loading Regime of a tight gas reservoir by coupling transient modelling of reservoir and wellbore.

A workflow is implemented in the software integrator RESOLVE which enables the coupling between a well and its multiple hydraulically fractured reservoirs. It ensures consistent results between the reservoir model and the transient well model in terms of mass flow rate, transient inflow performance and bottom hole flowing pressure. It also enables to visualize the cross-flow which occurs between the two reservoirs, and some water imbibition into the matrix during shut-in periods.

Tested on various reference wells, this new methodology represents properly the historical behaviour of the wells during steady-state flow and during self-killing periods. When modelling cyclic production, various shut-in / restart criteria can be handled by the workflow. It enables to optimize the average production of the wells and deliver some guidelines to the field operation teams. This is a great achievement compared with the need to implement long "cyclic production testing" campaigns.

Also, two-month coupled cyclic production modelling is performed at regular yearly intervals. Combining these long term production forecasts with the evolution of "average static pressure vs. cumulative gas production" derived from reservoir standalone long-term forecast, enables to compute reliable long term production forecast which accounts for cyclic production in liquid loading regime. The current results show significantly larger production than the one derived from usual decline curves.

Overall, the study is a leap forward in understanding transient well and reservoir interactions in order to improve field Estimated Ultimate Recovery. This field tested methodology can also be applied to many other situations when well instabilities interfere with reservoir transient behaviour (gas-lift heading, interference between unstable outflow and multi-layers inflow behaviour). To our knowledge, it is a "World First" of a coupling between a full commercial reservoir simulator and a commercial transient wellbore software.
A Working Condition Diagnosis Model of Sucker Rod Pumping Wells Based on Big Data Deep Learning
Authors: Wang Xiang , He Yanfeng , Li Fajun , Dou Xiangji , Wang Zhen , Xu Hui , Fu Lipei
Published: April 2019

Monitoring the working conditions of the sucker rod pumping wells in a timely and accurate manner is important for oil production. With the development of smart oil fields, more and more sensors are installed on the well. The variety and volume of the monitoring data are big. The oilfield big data can be utilized to improve the diagnostic performance. In this work, we aim to utilize the big data collected during oil well production and a deep learning technique to build a new generation of intelligent diagnosis model to monitor working condition of sucker rod pumping wells. Over 5 million of well monitoring records, which covers information about one year of an oil field block, are collected and preprocessed. To show the dynamic changes of the working conditions for the wells, the overlay dynamometer card is proposed and plotted for each data record. The overlay dynamometer card stacks two dynamometer curve at different times. Based on the overlay dynamometer cards, the working conditions are divided into 30 types, and the corresponding dataset are created. An intelligent diagnosis model using the convolutional neural network (CNN), one of the deep learning framework, is proposed. By the convolution and pooling operation, CNN can extract features of an image implicitly without human effort and prior knowledge. That makes CNN very suitable for the recognition of the overlay dynamometer cards. The architecture for working condition diagnosis CNN model is designed. The CNN model consists of 14 layers with six convolutional layers, three pooling layers, and three fully connected layers. The total number of neurons is over 1.7 million. The overlay dynamometer card dataset is used to train and validate the CNN model. The accuracy and efficiency of the model are evaluated. Both the training and validation accuracies of the CNN model are over 99% after ten training epochs. The average training elapsed time for an epoch is 8909.5 seconds and the average time to diagnosis a sample is 1.3 milliseconds. Based on the trained CNN model, a working condition monitoring software for suck rod pumping well is developed. The software runs 7×24 hours to diagnosis the working conditions of wells and post warning to users. It also has a feedback learning workflow to update the CNN model regularly to improve its performance. Through 3 months of on-site test run show that the actual accuracy of the CNN model is over 90%.
High Precision Velocity Model Building Technology for Gas Cloud Areas and its Application in P Oilfield, Bohai Bay Basin
Authors: Li Wenbin , Liu Lei , Wang Jianli , Liu Xuetong
Published: April 2019

As we all know, accuracy of the migration velocity determines the quality of imaging results to a large extent. However, traditional migration velocity analysis methods always fail in gas cloud area due to the complex wave field and poor quality of the seismic data. Aiming at this problem, we present a high precision velocity model building technology for gas cloud areas to improve seismic imaging quality in these areas. Diving wave always appears as first arrival and its ray density satisfies inversion demand well, which makes it easy to pick up shallow information and sensitive to velocity anomalies. Thus, we build velocity model for gas cloud areas based on both diving and reflected wave. Firstly, diving wave tomography inversion is carried out to establish a high precision velocity model of shallow layers. Then we perform reflection tomography inversion to get velocity model of deeper layers with shallow layers’ velocity model above as initial input. Finally, we build the accurate velocity model of gas cloud areas successfully.

The results of real data processing in P oilfield show that the velocity model built by our method has a better precision in gas cloud areas and matches the VSP velocity better in both gas cloud areas and normal areas. In contrast to the images based on conventional reflection wave velocity model, the imaging result based on our velocity model is obviously improved. Our method is widely applicable to the study of gas cloud areas and will help the understanding and interpretation of seismic data in gas cloud areas greatly.
Cohesive Approach for High-Resolution Seismic Using Inversion & Imaging in Malaysian Carbonate Field
Authors: Bashir Yasir , Babasafari Amir Abbas , Biswas Ajay , Hamidi Rositi , Moussavi Alashloo Seyed Yaser , Tariq Janjuah Hammad , Prasad Ghosh Deva , Weng Sum Chow
Published: April 2019

A majority of remaining proven Oil & Gas reserves is contained by Carbonate reservoir, and much more complicated to explore as imaging of the Carbonate rocks is poor. In case of Carbonate data, seismic diffraction imaging has contributed to an enhancement in the quality of seismic but there is still lack of understanding the lithology and impedance contrast which can be defined by the seismic inversion. In contrast, to the conventional process, an integration of seismic inversion methods are necessary to understand the lithology and include the full band of frequency in our initial model to incorporate and detail study about the basin for prospect evaluation. In this paper, an integrated approch is developed for better deleniation of subsurface structure and lithologies. Seismic post stack inversion technique is applied to the Carbonate field to study Electroficies and lithofacies of subsurface strata for better and detail study of the reservoir.
Application of an Integrative New Technique on Modeling and Numerical Simulation for Fractured Reservoir Based on Unstructured Grid: A Case Study of JZS Buried Hill Reservoir
Authors: Lv Zuobin , Huo Chunliang , Ge Lizhen , Xu Jing , Zhu Zhiqiang
Published: April 2019

JZS oilfield is an offshore metamorphic rock fractured buried hill oilfield. It was put into development in July 2010. The overall production situation of the oilfield is good, but some problems have been exposed. The main performance is as follows: It is difficult to accurately characterize the heterogeneity of fracture space distribution; In the numerical simulation of fractured reservoir, it is impossible to accurately describe and predict the fracture flow of fluid channeling in corner point grid system.

In order to solve the above problems, this study presents a new integrated fractured reservoir geological modeling and numerical simulation research method based on unstructured grid. There are three key aspects to this method. (1) The multi-scale (large, middle and small) discrete fracture system is established by combining outcrop measurement data with well point information and seismic attributes. On the basis of post-stack 3D seismic data, ants attributes are extracted, then the ant body results are transformed into large scale fractures; Using azimuth anisotropy attribute based on pre-stack inversion and combining the distribution orientation of large-scale fractures, the middle-scale fractures are established; According to the power law distribution relation between the cumulative frequency and the fracture length of large scale and small scale which based on outcrop observation, the imaging logging data and pre-stack inversion azimuth anisotropy attribute, small scale fractures are constructed by DFN technology.(2) For multi-scale fractures, the unstructured grid division technique is used to build a 3D model that conforms to the heterogeneity of dual media. In this study, a layered triangular prism grid generation technique is proposed. It is used to establish model of multi-scale fractures based on unstructured grid. Using large-scale fractures as a constraint, full 3D unstructured grid model is set up, and the discrete fracture model can accurately describe the fracture system and the coupling relationship between matrix and the fracture;(3)The triple-medium numerical simulation of the reservoir in the study area is carried out by using the automatic history fitting technology of ensemble kalman filter (EnKF). After several parameter adjustments, both the coincidence rate of the index and the fitting precision are higher than before.

Multi-scale discrete fracture model based on the large-scale fractures discretization processing, equivalent medium processing to middle and small scale fractures, keeps the seepage characteristic of the large-scale discrete fractures model and ensures the calculation efficiency. The results show that the new method has obvious advantages in computing speed and that the fitting effect is closer to the actual production performance.
Waterflood Surveillance by Calibrating Streamline-Based Simulation with Crosswell Electromagnetic Data
Authors: Mishra Shubham , Shrivastava Chandramani , Ojha Aditya , Miotti Fabio
Published: April 2019

Optimal exploitation of hydrocarbon reservoirs has always been a challenge due to uncertainties posed by subsurface heterogeneities that are often not factored into field development plans. Secondary and tertiary recovery mechanisms, such as waterflooding and enhanced oil recovery (EOR), are used to enhance the oilfield recovery beyond primary recovery. However, as the field development transitions to secondary/tertiary mechanisms, the challenges in monitoring these mechanisms further increase the uncertainty in field development. If these uncertainties are not reduced or incorporated properly, the field development may easily become uneconomic. This work presents a workflow that addresses the limitation of regular waterflood surveillance while characterizing the reservoir for optimal exploitation.

The current technologies for waterflood surveillance are limited either to local surveillance methods, such as tracers, crosswell seismic and crosswell electromagnetics (EM), or to uncalibrated global realizations, such as full-field streamline simulation, with no validation between the wells (It is to be noted that a full-field reservoir simulation calibrated with production-injection data in defined time-interval is stated as a global-surveillance method in this paper). This workflow devises integration of an effective local waterflood monitoring method, crosswell EM, and a global waterflood modeling method, streamline simulation. The process of validating the parameters of a geological model and a dynamic model with time-lapse crosswell EM data significantly reduces reservoir characterization uncertainty and helps in the preparation of a precise dynamic model.
Identification and Analogy of Carbonate Geometries Between Offshore Indus Basin in Pakistan and Proven Carbonate Play
Authors: Khan Muhammad Hanif , Maqsood Tahir , Jaswal Tariq Majeed , Mujahid Muhammad , Malik M. Suleman , Jadoon Ehtisham Faisal , Hakeem Uray Lukman
Published: April 2019

This article investigates the seismic reflection geometries (possible reservoir) of Paleogene of Offshore Indus Basin Pakistan (shelf area) from 2D seismic and make an analogue with the proven carbonate reservoir geometries found in countries such as Canada and Middle East.

The 2D seismic data are used to interpret the possible carbonate features and methods to identify them and define its depositional setting on the carbonate platform.

The offshore Indus Basin is tectonically a rift and a passive continental margin basin, located in Offshore Pakistan and Northwest India where carbonates were deposited on the shelf and the deep offshore area during early post-rift phase. In the deep offshore area, carbonates were set on volcanic seamounts during the Paleogene age.

In Paleogene, the Indian Plate was passing through the equator in the conditions of warmer water with appropriate water salinity, where those conditions were suitable for the growth of organisms responsible to develop reefs in the Offshore Indus area. The available seismic data analysis has indicated the possible presence of different carbonate reefs on the shelf. The seismic data enabled to define the possible carbonate Rimmed shelf depositional model in the area.

The aim of this article is to highlight and analogue carbonate seismic geometries, their internal architecture in the Paleogene interval of the Offshore Indus Basin (shelf area) and how to identify them, which may help for further exploration in Offshore Indus Basin.
Flow Enhancement by High Power Laser Technology
Authors: Batarseh Sameeh , AL Harith Abdullah , Othman Haitham , Al-Badairy Hameed
Published: April 2019

The objective of this work is to present the utilization of high-power laser technology in different downhole flow enhancement applications. High power laser technology provides innovative non-damaging technology and is an alternative to several current downhole conventional technologies. Wide ranges of high power laser applications have been identified, evaluated and successfully tested in the laboratory, these applications are related to improve production. The precision of controlling the laser parameters enables the properties flow improvement in all rock types.

Laser energy generated and transmitted from the laser source to the target via fiber optics cables. The laser beam is controlled by downhole tool and optical bottom hole assembly. Based on the identified applications, the laser tools are designed and built combining mechanical and optical components that are aligned and assembled accordingly, the tools released the final shaped beam to the target. The controlled beam generates thermal energy, this energy can melt, vaporize or spall the formation, depending on the application needed.

High power laser technology has the potential to change the industry in several downhole applications including perforations, heating, fractures initiation, open hole notching, deep perforation, and drilling. The motivation for searching for alternative technologies is the cost effective and advancement of the laser technology and the need for none damaging environmentally friendly alternative technology. Laser provides unique advantages for downhole applications, such as accuracy, precision, and power, these parameters have been successfully tested in the lab and the optimized setting are configured in the tool. Several iterations of the tools have been done to optimize and finalize the successful design. The tools are designed to fit in slim holes as small as four inches. In addition, the tools are designed to operate in a fluid environment, the tools are equipped with purging capabilities to circulate gas or fluid, the functions of the purging are to clean the hole from the debris and carry the cuttings.

The technology provides very small footprint and is environmentally friendly, it is a waterless technology when it is used for fracturing, and a non-explosive perforation base technology when it is used as a perforation gun. The unique futures of the technology are the precision is controlling and orienting the energy in any direction regardless of the reservoir stress orientation and magnitude. The precision in orienting the energy enables to focus the energy on the pay zones directly maximizing reservoir contact.
A New Multiple Chelating Acid System with Low Damage and Weak Dissolution
Authors: Li Nianyin , Yang Ming , Zhang Qian , Zhou Hongyu , Zhai Changjin , Feng Lei
Published: April 2019

Matrix acidizing is an essential strategy to maintain or increase productivity or injectivity of hydro-carbon wells. However, for loose sandstone reservoirs, the rock skeleton structure is easily de-stroyed by acidizing with conventional acid systems, which results in sand production. Also, the precipitation of metal fluorides, fluorosilicates, and so forth that may occur during acidizing will cause secondary damage to reservoirs. Therefore, we propose a new multiple chelating acid system (NMCAS) with low damage and weak dissolution. The system consists of multiple weak acids, organic phosphonic chelators, anionic polycarboxylic chelating dispersants, fluorides, and other auxiliary additives. Its performance was measured through laboratory tests. First, the dissolution retardation effect and dissolution capacity of NMCAS were analyzed by long-term dissolution tests. Then, the changes of particle size and mineral composition of the rock powder before and after dissolution of NMCAS and a regular mud acid system were comparatively analyzed by a sieving analysis method and x-ray diffraction measurement. Third, the chelating abilities of the system on metal ions were analyzed by a titration method. Moreover, the improvement of seepage capacity was analyzed by a core acidification flowing experiment and scanning electron microscopy. Finally, the dissolution mechanism of the system was further analyzed by energy dispersive spectroscopy. Research results indicate that NMCAS has a good retardation effect and a moderate dissolution ability. After dissolution of rock powder with the proposed acid system, the changes in particle size were less than those of the conventional mud acid system. Also, it dissolved merely a small portion of the clay minerals, but increased the dissolution of quartz, feldspar, and other matrices. NMCAS can prevent secondary precipitation of metal ions during the acidizing process because of its strong chelating ability for calcium ions, magnesium ions, and iron ions. The permeability of sample cores was moderately increased, and they formed obvious dissolution channels; however, the rock skele-ton structure was not destroyed after acidizing with NMCAS. This is because the system reduced the dissolution of clay minerals with larger specific surfaces because of the adsorption effect (a relatively lower reduction in the content of the Al element) while enhancing that of such matrices as quartz and feldspar (relatively larger changes in the content of the Si element). NMCAS can dis-solve the cement appropriately while enhancing the dissolution of the matrices, which protects the rock skeleton structure of loose sandstone reservoirs. The proposed acid solution would be of value for removing formation plugging and increasing the production of loose sandstone reservoirs.
Linking Injection-Induced Seismicity to Permeability Changes
Authors: Zhang Xi , Zhang Fengshou , Wang Shize
Published: April 2019

The permeability along a fracture is not constant, but varies with geometrical complexities such as pre-existing cracks. The spatial permeability changes affecting fluid pressure distributions can generate a sophisticated source mechanism potential to interpret measured seismicity complexity in the field. In this study, the relation between injection-induced seismicity and changes in fracture permeability during hydraulic fracturing stimulation of naturally fractured reservoirs is investigated numerically. In the model, the infinite homogeneous rock is assumed to be impermeable and elastic and a plane-strain fracture is embedded in it with distributed cracks. The fluid flow in the fracture is realized through over pressure generated by constant-rate injection. When the over-pressurized fluid enters these cracks, the pressure varying trend is changed and the injection pressure tends to increase, rather than decrease monotonically. Also, the slipping is temporarily stopped along the whole fracture. When the barrier to fluid flow is overcome, a most prominent pulse-type slip at a limited slip speed occurs along the pressurized region. The slip pulse can induce an injection pressure drop reflecting the decrease of the stress level near the rupture tip. In the meantime, the slip pulse acts as the source mechanisms for these microseismic events during the fracturing stimulation operations. It is found that the stress drop and slip rate decrease with rupture growth. In addition, the stopping phase and the accelerating duration of the slip patterns are two interesting features to estimate the source sizes of the rupture complexities generated by the forced fluid flow along a fracture.
Effective Annular Ledge Formation Sidetracking in Multilateral Wells in Vostochno-Messoyakhskoye Field
Authors: Voronin Andrey , Abaltusov Nikolay , Vershinin Anton , Dmitriev Aleksandr
Published: April 2019

Multilateral drilling technology offers a highly effective method of enhanced oil recovery in fields characterized by complicated geological structure. This paper describes the analysis of sidetracks in an open hole by annular ledge formation with the use of a downhole motor in multilateral wells in Vostochno-Messoyakhskoye field.

Since May 2018, more than 130 sidetracks have been drilled in Vostochno-Messoyakhskoye field with the use of bottomhole assembly (BHA) with a downhole motor in open hole by annular ledge formation. The fundamental difference between this method and conventional sidetracking with a downhole motor is that during sidetracking the entire drill string constantly rotates, rather than just bit rotation produced by downhole motor operation. In the process of technology introduction a comparison was made on how different downhole and geological conditions influence the time and performance results.

The technology introduction resulted in the sidetracking time reduction from 9 hours to just 3 to 4 hours.

A number of additional advantages of sidetracking with annular ledge formation were confirmed in the process of operations:

The constant rotation of the drill string enables smooth weight transfer to the bit smooth, without failures. This contributes to effective and uniform ledge formation. Such sidetracking can be carried out at an extended length of open hole when it is difficult to ensure a free movement of the BHA which is necessary of conventional sidetracking. Constant rotation mitigates the risk of differential sticking. More favorable conditions are created for BHA movement in an interval of the holes diversion and subsequently for liner running in. It is possible to sidetrack with the use of a stiff BHA including a complete set of logging tools. In case of conventional sidetracking, it is preferable to use a short and flexible BHA.

The experience gained in Vostochno-Messoyakhskoye field can be extrapolate to other fields where multilateral wells are drilled with annular ledge formation.