bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of a Barrier Integrity Violation Risk Using an Integrated 4D Reservoir Geomechanics Study
Authors: Sadykov Lenar , Korelskiy Evgeny , Samohvalov Andrey , Kostina Anna , Mamedov Elmin , Khromova Elizaveta , Zhelezova Anna , Shtun Sergey Yu. , Alexeev Andrej G.
Published: October 2018

Hydrogen sulphide represents an undesirable component of hydrocarbon reservoir fluids and its presence poses not only a significant risk for health and life of a personnel involved in hydrocarbon production and transportation, but also may drastically affect the field development strategy and economics, especially in an offshore environment.

The paper demonstrates the results of an assessment of risk of a hydrogen sulfide-containing gas breakthrough into the upper reservoir during its development at one of the fields of the Caspian oil and gas province. The assessment was performed using a coupled reservoir geomechanics modeling that allowed to estimate the changes in in-situ stresses state with field development. During production, differential and non-uniform pressure changes, caused by different depletion levels, result in differential deformation due to the change in effective stress, leading to reservoir rock failure, reservoir compaction and ground surface subsidence. Excessive localized deformation may also result in potential issues in cap and underlying rock integrity and fault seals.

A comprehensive mechanical core testing was carried out to correctly describe the rock failure criteria, which revealed the behavior of upper-layer cavernous carbonates similar to the behavior of the chalk formations of the North Sea, which are known to be prone to significant compaction during field development (J.P. Johnson et al, 1988).
Gas Adsorption Modeling in Multi-Scale Pore Structures of Shale
Authors: Zhang Yizhong , Wang Xiangzeng , Yao Shanshan , Yuan Qingwang , Zeng Fanhua
Published: October 2018

Shale pore space has a wide distribution of sizes (nm-μm) and complex configurations. Better knowledge of gas adsorption characteristics in real pore space is crucial for estimating shale gas-in-place. We develop a novel methodology to accurately and effectively calculate gas adsorption isotherms in multi-scale pore networks that simulate real pore structures inside shale. The influence of water saturations (in kerogen and clay) and pore distributions on gas adsorption is examined with our new model. 3D pore networks which connect both mesopores (2-50nm) and macropores (>50nm) are developed based on 2D SEM images and mercury intrusion analysis. Interparticle pores and pores inside kerogen have different morphologies from the pores in clay agglomerates in our pore networks. The gas adsorption on each dry pore/throat's surface is realized by capillary condensation with the Kelvin equation, which relates capillary condensation to pore/throat structure, different solid (clay and kerogen) surface characteristics and fluid properties. Moreover, we use the gas-liquid Gibbs adsorption model for gas adsorption on wet solid surfaces with water present, which is not considered in the literature. 3D pore networks and nitrogen adsorption isotherms are generated for the Silurian Longmaxi Formation shale samples. The simulated nitrogen adsorption isotherms are comparable to adsorption test results. The comparison confirms that both accurate adsorption modeling on pore surfaces and reliable pore space reconstruction are important for designing and analyzing adsorption measurements. Sets of methane adsorption isotherms are further calculated on different pore networks. Each pore network is assigned a unique combination of clay content, total organic carbon content and pore size distribution (PSD). When the pore volume is constant, shale has higher adsorption amount of methane with decreasing pore sizes. When the water saturation increases, water will first occupy the void space in clay from small pores to large pores and then extend to pores inside kerogen. It is concluded that the adsorption amount of methane could be significantly reduced by 50% when water saturation in pore space increases from zero to 30%. Different from previous adsorption modeling studies on single dry pore/throat or a bundle of dry tubes, this study considers the adsorption modeling on a pore network that connects pores and throats with different sizes, wet or dry surfaces and various morphologies. This methodology and simulation results are reliable and effective for fundamental study and field performance estimation of gas adsorption in shale reservoirs.
Geomechanical Modeling Under Industry Standards
Authors: Cheremisin Aleksandr , Petrakov Yuri , Sobolev Aleksei , Stishenko Sergei , Tatur Olga , Chettykbaeva Kamilla , Ocheretyanyy Anton
Published: October 2018

Geomechanical modelling is widely applied in projecting oil and gas field development. Geomechanics are essential to three basic approaches: supporting oil and gas wells drilling in order to reduce the risk of hole instability (one-dimensional geomechanics).an adequation of effective stress of the reservoir occurs in the process of oil and gas field development. Stress condition changes modelling allows to consider their influence on the development parameters (three-dimensional geomechanics).preparing FRAC design and subsequent forthcoming debit appraisal.

Despite the wide expansion of geomechanical modelling some oil and gas producers do not apply it, considering it useless waste of resource. Even though vast experience shows that conducting certain research programs and developing geomechanical models can considerably increase drilling and development process efficiency. Furthermore, laboratory test and calculation expenses are materially lower than potential losses. But implementing new technology (geomechanical modelling in particular) to efficient oil and gas production processes is not always simple since it is necessary to justify the currentness of additional expenses and unevident profit.

Apart from the difficulties in slow implementation there is a variety of new companies that offer geomechanical modelling service. Each company offers its own approach to core examination, to specifying necessary number of samples and to the process of modelling. The customer has to choose the optimal technology of geomechanical modelling. Still the methodological basis of core examination must be settled plainly.

Therefore geomechanical modelling, an essential element of field development project documentation, has no standards or regulations which makes it hard to evaluate the prediction calculations.

The study addresses the question of necessity of regulation/standardization in geomechanical modelling at the government level (as with regulating the development plan and the calculation of reserves).
Early Kick Detection Using Adaptive Analytics with Downhole Accelerometer Data
Authors: Samuel Robello
Published: October 2018

High frequency downhole vibration data includes more hidden information than low frequency surface data. This paper discusses monitoring high frequency acceleration data for early kick detection because the accelerator sensor values’ trend is monitored rather than processed.

When gas, fluid, or oil kick occurs, fluid influx reduces fluid viscosity in the annulus, causing degradation of the damping factor. The sensor installed on the drillpipe detects the velocity/acceleration modification, resulting in the damping factor modification and includes an analytical model to calculate the effect of the damping ratio on the acceleration calculations. Fluid influx and migration in the wellbore strongly affects the damping factor.

This paper discusses a method of deconvoluting sensor values that use a combination of minimum entropy deconvolution and the Teager-Kaiser energy operator to remove the noise, unwanted sensor values, and the likelihood of false predictions. The trend of the final intrinsic mode functions (IMFs) at each depth is continuously monitored to predict formation influx, if any. A novel concept of monitoring incremental IMF and IMF energy at each depth is introduced, revealing a wealth of information and simplifying the process of monitoring and analyzing the vast amount of available data. The methodology developed extracts essential information from high frequency vibration data to make real-time data monitoring straightforward, reliable, and fast.
Drilling Performance Improvement in Marcellus Shale Play: A Case Study of Successful Implementation of Real-Time Digital Solution
Authors: Rimmey Andrew , Han George , Poojari Asha , Atwal Harnam
Published: October 2018

Most US onshore shale operators work with extremely limited budgets to be profitable in a low margin, low oil price environment. There is a significant emphasis on footage drilled per day, with solutions like better well plans, drill bits, and innovative bottom-hole assemblies (BHA). However, the smaller activities that add up to achieve higher footage per day include weight to weight (W-W) and connection times. The traditional ways to measure these key performance indicators (KPIs) and identify operational inefficiencies are manual, time consuming and after-the-fact.

To increase the overall drilling performance even with proven BHAs, an operator in Marcellus Shale leveraged a web-based application using industry-standard wellsite information transfer standard markup language (WITSML) protocol for automatic real-time drilling performance KPI monitoring and advisory services to focus on standardizing and reducing the W-W time. Weight to Weight time was divided into weight to slip (W-S), slip to slip (S-S) or connection times, and slip to weight (S-W) times to analyze trends and practices during the drilling process. The study focused on average W-W time improvement, and operational consistency on two rigs while drilling 32 wells from seven pads.

During this continuous improvement process, the operator identified best crew performance using automated crew comparison KPIs and disseminated best practices among the crews. At the end of the study, one rig W-W goal attainment rate increased by 50%. The operator also worked with the rig contractor to shuffle the rig crews by including the competent personnel from the most-efficient rig crew to the less-efficient rig crew to accelerate the sharing of best practices. This approach led to a 19% improvement of average W-W time over the course of the drilling campaign, and improved overall drilling performance. The best well was used for benchmarking and updated throughout the drilling campaign for continuous improvement of drilling performance.

Digital technologies combined with existing proven downhole technologies can help identify operational inefficiencies. Operators that use remote operations centers for planning, execution and risk reduction can benefit from real-time monitoring of drilling KPIs by taking timely and proactive measures.
Cost Reengineering
Authors: Maksimov Yuri , Skudar Oleg , Yanina Irina , Pashkevich Lev , Sandler Ilya , Ulyaschenko Vladislav
Published: October 2018

This article presents the method developed by Gazprom Neft to systematically improve efficiency of reserves of mature assets through the use of automated and integrated modules designed for comprehensive calculation of surface infrastructure construction and maintenance costs. A new and relevant for the oil and gas industry term – cost reengineering is suggested and its definition is given.

Best practices of cost engineering/reengineering are tested within the framework of some integrated reengineering projects implemented at Gazprom Neft's petroleum fields. The automation of the capital and operating costs estimation process contributed to the rapid consideration of a significant number of production optimization scenarios, and the high degree of decomposition of cost items and their formation parameters made it possible to manage costs in the context of individual elements of field infrastructure facilities.

The result of the efforts made by the multidisciplinary team was the development of a step-by-step workflow for reengineering projects which allows, in a systematic and integrated manner, to identify constraints and form the matrix of optimization measures.
Core Cleaning and Aging Effects of Devonian Carbonate Core at Micro Scale
Authors: Kovalev Kirill , Rashkovskiy Alexander , Khayrullin Marsel , Grishin Pavel , Shklover Vladimir , Artemov Nikita , Maryasev Igor
Published: October 2018

A carbonate core from Timan-Pechora oil and gas province study of some core cleaning and aging procedures on composition and structure of a pore space-mineral fringe are an important task for reserves evaluation and oil recovery modeling. Oil mineral skeleton interaction at micro scale characteristics provided by modern methods of electron microscopy and spectroscopy, that have allowed to extend a traditional petrophysic core data of reservoir properties and wettability. The Devonian Timan-Pechora carbonates hydrocarbon films and chemical bonds analysis novel data was obtained by a XPS technique taking into account pore volume structure, films microscopic structure and chemical behavior at calcite mineral surface. Carbonate rock cleaning and aging procedures impact was carried out.

The evaluation of the influence of the extractant type on the intensity of the impact on the rock and the regimes of aging and storage of the core on the microstructural parameters of the sorption of hydrocarbon films on the surface of the void space made it possible to develop recommendations for preserving the character of the wettability of the initially hydrophobic carbonate rocks for further petrophysical experiments and the development of an EOR. The hydrophobic carbonates wettability characteristic preservation recommendations proposed basing on hydrocarbon films microstructure sorption on mineral surface parameters. A water hydrophobic carbonate rock interaction conclusions were proposed basing on data correlation about carbon chemical bond types, microstructural studies, water microdrops dynamic condensation on rock surface analysis combined with reservoir properties and pore volume distribution parameters about the hydrocarbon films sorption and impact. This type of rocks data clarifying practices for EOR forecasting proposed.
Optimization of Well Placement in Waterfloods With Optimal Control Theory Under Geological Uncertainty
Authors: Temizel Cenk , Zhiyenkulov Murat , Ussenova Kamshat , Kazhym Tilek , Canbaz Celal Hakan , Saputelli Luigi Alfonso
Published: October 2018

Optimum well placement in intelligent fields, using previously developed optimal control methods to maximize net present value (NPV), is becoming practical with recent advances in technologies as well as their applications to the petroleum industry. To efficiently use these methods in an intelligent field, an assessment of its economic aspects and its performance, especially in reservoirs with high degree of heterogeneity (uncertainty), must be made. By using such integrated workflows, mature and new field can be developed better. The workflow could be used as a reliable tool for improving the decision-making process.

There are multiple optimization techniques used in the industry for optimizing well placement (e.g. direct and gradient optimization). With the use of reservoir simulation case study, this paper aims to provide a comparative performance analysis of multiple optimization techniques. To make the evaluation stronger and more application to a real-world problem, the model selected for this study has a high degree of geological uncertainty and constraints for computation time, infrastructure and complexity to decide on optimal well placements.

Having a better understanding on the uncertainties in geology lead to more robust decisions in reservoir management. Right strategy especially helps in optimizing larger scale, million-cell model simulations enabling practical implementation of reservoir simulation coupled with optimization.

Optimum well placement in complex reservoirs requires a complete grasp of optimization methods, key factors and constraints but most importantly the effect of geological uncertainty. A lack of awareness of optimization algorithms and their applications by engineers is a drawback in this process. In addition, complete evaluation of geological uncertainty is another challenge. This study provides an understanding and clarification to serve as a guideline on optimization practices by outlining the significant components in the process.
A Novel Approach to Barrier Integrity Testing in Well
Authors: Stein Arild
Published: October 2018

Verification and testing of a newly installed wellbore barrier, in older assets has proven to be challenging. Even more so when the well has structural issues, indemnities or weak spots in the barrier envelope, or weakend well construction that limits the possibility to acheive a positive pressure verification of the barrier with an applied surface pressure versus the reservoir pressure.

A suitable location with necessary support and strength should be located in the well. If installing a mechanical barrier in means of a bridge plug as the primary barrier, we will monitor the installation forces in the anchoring and sealing sequence. This individual signature will be verified towards a nominal base line signature of a ISO approved test and a library of thousands of collected installation profiles. Any abnormality can trigger a release and relocating of the barrier. A second verification barrier will then be installed close above the primary barrier and installation sequence will be verified the same way as the primary barrier. When both installation signatures are accounted for we can pressure test the installed barriers. This can be done with a pressure manipulation tool, where we introduce a calculated predetermined pressure drop between the installed primary barrier and the verification barrier above. By monitoring this pressure alteration vs. the pressure above the verification barrier, we can determine if we have a verified primary and verification barrier.

The Primary Barrier is verified in the direction of flow (negative pressure test). And verification barrier as the secondary barrier is verified with a positive pressure test. If a dual barrier is requested you can leave the verification barrier as secondary barrier or pull to re-use.
The Complex Approach to Seismic Researches at Studying of a Nonconventional Reservoir
Authors: Konushenko Alexander , Kovalenko Maxim , Shkrabov Andrey
Published: October 2018

Development of methodical techniques for performing seismic studies in complex geological environments and the sequence of their application for the study of an unconventional reservoir. Evaluation of seismic prospecting capabilities for detailed study of the structure of a specific area and subsequent justification for 3D seismic survey.
The Viability of Gas Injection EOR in Eagle Ford Shale Reservoirs
Authors: Atan Safian , Ajayi Arashi , Honarpour Matt , Turek Edward , Dillenbeck Eric , Mock Cheryl , Ahmadi Mahmood , Pereira Carlos
Published: October 2018

Gas Injection, Huff-and-Puff Enhanced Oil Recovery (EOR) technique have the potential to improve liquid hydrocarbon recovery in ultra-tight, unconventional reservoirs. This paper studies the technical and economic viability of this EOR technique in Eagle Ford shale reservoirs using natural gas injection – generally after some period of primary depletion, typically through long horizontal reach wells that were hydraulically fractured.

To achieve this, three primary steps were undertaken: First, a series of multi-well, compositional simulation models were constructed, calibrated with lab data, and history matched for an extended production period. This effort characterizes a set of equiprobable combinations of fracture and matrix properties, as well as the parametric description of the stimulated reservoir volume. Second, these history matched models were then used to numerically simulate the Gas Injection Huff-and-Puff EOR process to determine a set of optimized operational variables (operating pressures, injection pressure, cycle durations, the corresponding injection rate, and slug size). The results were also sensitized to the effect of geomechanics, containment, as well as the effect of diffusion. The primary source of information that feeds the sensitivity analysis was derived from laboratory work investigating the EOR processes at the core scale. The third and last step, economic analysis was performed using calibrated rate profiles to assess the impact of initial yield and the amount of depletion on value. Resulting analysis provided insight to the economic viability of the EOR deployment at field-scale.

Results show that the recovery factor uplift, all things being equal, is a function of the original yield, the amount of depletion, and the minimum operating pressure during the production cycles. In reality, however, equally as critical to the success of an EOR project is the formulation of the deployment strategy - the timing of the development start (forecasted price environment), pad selection, compressor scheduling, injection-soak-production durations, surveillance plans, and mitigation strategies (for poor containment and inefficient compressor utilization).

The workflow utilized in this paper both characterizes the uncertainties in an EOR project in the Eagle Ford and provides insight into operating conditions and surveillance recommendations. This is the key for a successful demonstration pilot which can then lead to a field-scale EOR deployment.
Arctic Zone of the Siberian Platform - Resource Base and Development Potential
Authors: Dmitrievsky Anatoly , Eremin Nikolai , Shabalin Nikolai
Published: October 2018

The interest of oil and gas companies in the Arctic region of the Earth, despite the difficulties in the geological exploration, the development and the exploitation of discovered fields, in access to markets for the produced hydrocarbons is quite high. According to the US Geological survey, the subsoil of the Arctic zones of five coastal States – the United States, Canada, Russia, Denmark and Norway – contains at least 525 billion BBOE (barrels of oil equivalent) or 75 billion tons, including the subsoil of the Arctic zone of Russia – 315.4 billion BBOE (26). The Arctic zone of the Eastern Siberia is characterized by a harsh climate (in winter the temperature drops below −60 °C on land and to −40 °C at sea), the presence of the permafrost, the lack or remoteness of the infrastructure for the delivery of the necessary equipment and materials, the transportation of produced hydrocarbons, short periods of the field work from November to April on land, from July to September at sea (6, 7, 25). The basic concepts of the geological and tectonic structure and the oil and gas content of the land and the adjacent shelf of the Arctic zone of the Siberian platform are based on the seismic data, tied to the existing deep parametric and exploratory wells. To date, five regional seismostratigraphic complexes have been identified and described: the Mesozoic-Cenozoic, the Permian-Lower Triassic, the Upper-Middle Paleozoic, the Upper Proterozoic-Cambrian and the surface of the basement. The evaluation of the potential hydrocarbon resources was carried out in the Yenisei-Khatanga, the Anabaro-Khatanga, the Anabar-Lena and part on the Laptev Sea oil and gas regions.
Subsea Well Integrity - Permanent Monitoring Solution to Verify Critical Well Barriers, Simplify and Reduce Cost of Periodic Testing
Authors: Grimstad Sverre
Published: October 2018

This paper will focus on well integrity standards and give practical examples on how they are applied for wells in the Norwegian Sea.

Further the paper will review how the standards are used for testing and verifying barriers in a well, and how well integrity on subsea and TLP (tension leg platforms) benefit with the introduction of annulus B monitoring.

Examples will present how barriers can be moved and testing time reduced, while still complying to standards and local regulations as well as making the well design more robust.

Data from a well using the annulus B monitoring system will be presented and explained to give an understanding how this can benefit subsea wells throughout life of well.
Minimization of Risks in Reservoir Prediction Based on Seismic Data
Authors: Vasilyev Mikhail , Butorin Aleksandr
Published: October 2018

The article reviews a fast-track high-quality evaluation approach to the net pay reservoir thickness in a well-to-well space. The review is based on rocks the upper-Jurassic (J1-1) Vasyugan suite exemplified by two areas in Western Siberia.

The presence of certain geological prerequisites for reservoir formation supported by the use of historical data analysis made it possible to cluster the area in question interest according to the level of confidence in the availability of net pay thicknesses.

The approach described in the article has been instrumental in optimizing the drilling program by mitigating cost risks. New wells delivered corroborating evidence of data reviewed.
Application of Formation Pressure While Drilling FPWD Technology in Challenging Low Mobility Environment – Case Study from Western Kazakhstan
Authors: Ramatullayev Samat , Makhmotov Akikat , Zhabagenov Muratbek , Ospanov Dastan , Markelov Yura , Navrotsky Alexander , Gabdyzhamalov Yerlan , Nurgaliyev Ruslan , Maletti Giorgio , Assanova Tatyana
Published: October 2018

Historically, pressure measurements have been performed with wireline formation tester (WFT) tools. In highly deviated and horizontal wells, wireline tools are drill-pipe conveyed and this operation can be complex and adds significant expenses and operational risks. On the other hand, formation pressure while drilling (FPWD) technology minimizes operational risks at reduced overall cost and results in increased operational efficiency. This is particularly true for highly deviated and horizontal wells.

FPWD technology has its own application envelope. Low permeability reservoirs are traditionally considered to be "no-go zone" for FPWD. Reason being nearly all FPWD tools on the market are equipped with a single probe that has a modest flow area. Whenever formation exhibits extremely low mobility, in the order of 0.1 mD/cP or lower, operators prefer to opt for configurations that increase the flow area such as dual packer conveyed on wireline, despite the added cost and conveyance risk. However, proper job planning and real-time data transmission allows to acquire critical reservoir dynamic data with FPWD tool in challenging low-permeability environment in horizontal wells with reduced operational risks.

The following paper discusses the first successful application of FPWD technology in horizontal wells drilled in low permeability giant carbonate reservoir located in Western Kazakhstan. It focuses on the approaches taken during job planning and execution, dwells upon the acquired results and offers a methodology on how to optimize the acquisition. It is worth noting that fluid mobility in some stations was below 0.1 mD/cP, making it an extremely challenging environment. Nevertheless, the results acquired in eight wells has proven that FPWD can perform effectively and provide crucial reservoir dynamic data in separate clinoforms and gain insights about reservoir depletion mechanism, which was previously inaccessible due to operational risks related to formation tester tools conveyance in horizontal wells.
Best Practices of Assisted History Matching Using Design of Experiments
Authors: Li Boxiao , Bhark Eric W. , Gross Stephen J. , Billiter Travis C. , Dehghani Kaveh
Published: October 2018

Assisted history matching (AHM) using Design of Experiments (DoE) is one of the most commonly applied history matching techniques in the oil and gas industry. When applied properly, this stochastic method finds a representative ensemble of history-matched reservoir models for probabilistic uncertainty analysis of production forecast. Although DoE-based AHM is straightforward in concept, it can be misused in practice because the workflow involves many statistical and modeling principles that should be followed rigorously.

In this paper, the entire DoE-based AHM workflow is demonstrated in a coherent and comprehensive case study that is divided in seven key stages: problem framing, sensitivity analysis, proxy building, Monte-Carlo simulation, history-match filtering, production forecast, and representative model selection. Best practices of each stage are summarized to help reservoir management (RM) engineers understand and apply this powerful workflow for reliable history matching and probabilistic production forecasting.

One major difficulty in any history matching method is to define the history-match tolerance, which reflects the engineer's comfort level of calling a reservoir model "history-matched" even though the difference between simulated and observed production data is not zero. It is a compromise to the intrinsic and unavoidable imperfectness of reservoir model construction, data measurement, and proxy creation. A practical procedure is provided to help engineers define the history-match tolerance considering the model, data-measurement, and proxy errors.
Refracturing of Multistage Horizontal Wells in PJSC Gazprom Neft
Authors: Ogorodov Alexey , Ostashuk Anatoly , Barkalov Stanislav
Published: October 2018

Since 2011 most newly commissioned wells at Gazprom Neft fields are horizontal (Hz), subjected to multi-stage hydraulic fracturing (multi-stage frac). To date, about 1,300 horizontal wells with multi-stage frac, equipped with packer-port liner assemblies (non-cemented), ball- activated, including about 800 wells equipped with single-action fracturing collars, have been drilled at the Company's fields.
Retrospective Analysis of Hydrofracturing with the Dimensionless Parameters: Comparing Design and Transient Tests
Authors: Shel Egor , Paderin Grigory , Kabanova Polina
Published: October 2018

Due to the frequent application of hydraulic fracturing technology (HF) on oil and gas fields, there is a large amount of statistical information about the operations carried out. It is possible to make a conclusion about the efficiency of the hydraulic fracturing, consider the design changes and make recommendations on the basis of results of data processing. However this task becomes complicated because conduction of pressure transient analysis on fracking wells reveals that the values of the fracture parameters, in particular the half-length, significantly differ from those planned for design.

This paper is devoted to the investigation of the possible reasons of this discrepancy by using dimensionless variables, which allows analyzing of information about the performed fracturing operations. The nondimensionalization of the basic equations using for the hydraulic fracture modeling made it possible to obtain the dependence of the dimensionless half-length of the fracture on the dimensionless volume of the injected liquid, and also to obtain an empirical formula for estimating the half-length of the fracture. Also, the analysis provides a possibility to exclude the influence of different factors that could make a significant contribution to the existing discrepancy.

As a result of the analysis, limitation of PTA models, related, for example, to the non-uniform fracture conductivity and the lack of interflow between layers with different properties, as well as the fracture design errors associated with incorrect closing ratios are identified among the most probable causes of the fracture length difference.
A Comprehensive Approach to Improve the Efficiency of MSF is Implemented in PAO Gazprom Neft
Authors: Kazakov Evgeny , Sayfutdinov Elnar , Bukharov Dinar , Fayzullin Ildar
Published: October 2018

A rather challenging situation in the oil and gas industry requires to improve the efficiency of field development models and reservoir stimulation methods (EOR). An important factor that determines an effective model is an increased oil recovery factor at the Gazprom Neft fields and additional oil production with a commensurate increase in costs. To improve the oil recovery factor, the first step was to drill new horizontal wells and sidetracks with a horizontal ending which allowed increasing the contact area of the well and the reservoir and involved new reservoir zones into the development, increasing its oil recovery. However, drilling of new horizontal wells and sidetracking alone, without the introduction of advanced completion technologies, does not allow to achieve the desired result and maintain the production rates.

Currently, many service companies have their own research centers and offer a huge amount of technologies, but in fact such technologies have not been tested at reservoir conditions of Russia's oil and gas fields. The main challenge is the development and implementation of new technological solutions within modern business strategies for completing wells with multi-stage frac assemblies.

The Company's teams have studied the world experience and the offers of service companies in the field of horizontal and multi-stag frac completion technologies, as well have analyzed all the proposed solutions and model history matching applied worldwide with regard to the Russian reservoir conditions. In many practical cases, the application of successful foreign technologies provided by the service companies at the conditions of Russian fields turns out to be "raw". To achieve success, an additional comprehensive development of technologies is required at the planning stage with regard to the field conditions and the Standards requirements. New organizational forms have been introduced to work out the entire range of activities, from drilling to pre-production of each specific well, which allowed, jointly with the Contractor, to run a virtual simulation and to implement the scheduled operations at the preparation stage, taking into account the existing experience of all subsidiaries: the scheduled well interventions, the analysis of possible risks at the preparation and implementation stages. Such comprehensive approach, as well as new organizational forms, virtual modeling and implementation of scheduled operations resulted in the following: accident-free execution of scheduled operations, strict schedule compliance, reduced time costs, new technical and technological solutions.
A New Productivity Prediction Hybrid Model for Multi-Fractured Horizontal Wells in Tight Oil Reservoirs
Authors: Tao Liang , Guo Jianchun , Zhou Xiaofeng , Kitaeva Alena , Zeng Jie
Published: October 2018

Productivity analysis relates to the quantitative evaluation of factors for individual members as well as to their comprehensive influence. It is difficult to describe the nonlinear relationship of various factors. A novel and original combination of grey relation analysis (GRA) and fuzzy logic productivity prediction hybrid model is proposed in this study to solve the problem. First, based on the parameters of the constructed wells, several elements were chosen as appraisal factors. The multi-level appraisal system was established to describe the nonlinear relationship of various factors. Then, GRA was used to calculate the weight factor and determine the main factors that influence the result of multi-fractured horizontal wells (MFHWs). Finally, coupling GRA with fuzzy logic to calculate the comprehensive evaluation score (CES), which is used to predict productivity and determine the classification value of the reservoir to evaluate the reservoir quality. The hybrid prediction model has been successfully applied to 18 wells of the tight oil field in Northeast China. Practical application results demonstrated a good agreement between the measured initial production and the output of the hybrid model. The new model can be used to predict production for MFHWs quickly and economically.
Technological Development of Hydraulic Fracturing in TATNEFT's Carbonate Reservoirs. Experience in Engineering Design, Monitoring and Management of Fracture's Geometrical Parameters
Authors: Khusainov Ruslan , Kochetkov Aleksandr , Garifullin Rustem , Sirazdinov Vagiz , Ganiev Bulat , Lutfullin Azat
Published: October 2018

Nowaday, more than half of the residual oil reserves in PJSC Tatneft are concentrated in carbonate reservoirs, while the share of their production is lower than in terrigenous sediments (Figure 1).

This determines the set of challenges facing PJSC Tatneft in the field of stimulation of oil production from carbonate reservoirs. The work is devoted to the search for the best solutions for the selection, design and implementation of various types of fracturing (acid, propane, hybrid) in carbonate reservoirs. A qualitative and comprehensive assessment of the applied technical solutions and tools for monitoring the implementation of hydraulic fracturing is given.
Experience and Optimization of Essential Multistage Fracturing Technology with Coiled Tubing at the Well for the Vinogradova Oilfield
Authors: Parshin Nikolay , Burdin Konstantin , Starodubtseva Ksenia , Novikov Maxim , Demkovich Mikhail
Published: October 2018

In the article presented 2 years of experience gained during multi-stage hydraulic fracturing (MSF) on 17 wells, by means of coiled tubing (CT) without lifting it to the surface, performed in years 2017 – 2018 on Vinogradova oilfield, KhMAO, Russia. In 2017 it was successfully implemented innovative technology, where fracturing operations are combined with coiled tubing (CT) operations and are run together with CT inside the well. Current method is based on operating reusable fracturing ports, where opening and closing is carried out using coiled tubing with subsequent performace of MSF along the CT/Tubing annulus. During these jobs, considerable experience was gained, the technologies were optimized and raised issues solved, including excessive abrasive wear of the coiled tubing pipe, leaks, etc.

Vinogradova oilfield is a unique oil-saturated low-permeable reservoir with a small effective thickness, characterized by considerable stratification and gas-saturated porous layers.

MSF technology demonstrated high efficiency and proved its reliability. Starting from February 2017 till June 2018 it was 17 wells accomplished, where 246 fracturings were carried out. All the wells were successfully commissioned. The implementation of innovative approaches to multi-stage hydraulic fracturing while coiled tubing remains in the well, resulted in 2-fold work time reduction, while the amount of frac ports doubled per well. The time frame of CT work between fracturing stages was minimized from 4 to 1.5 hours. During the job on one of the wells, it was encountered a leak in the completion (liner) in the shoe area, in order to continue MSF job, the isolation packer was run and temporary installed, which allowed to accomplish the operation.

The performance of MSF technology without lifting coiled tubing to the surface proved its efficiency and economic feasibility, becoming more and more popular among operating companies, it has great potential for future implementation both in Russia and in the rest of the world. The area of distribution and application of MSF using CT is growing every year, the most relevant technology found in oil fringe with a gas cap or bottom water. The accumulated experience in this project creates the basis for the wide introduction and application of technology on other projects
Analysis of Time-Dependent Behavior of Dynamic and Static Parameters of Preheated Westerly Granite for Microseismic Fracture Monitoring Experiments
Authors: Dotsenko Artyom , Stukachev Vladimir , Andrade De Carli Jean Carlos , Shevtsova Anna , Charara Marwan
Published: October 2018

A detailed analysis of time-dependent and strain-dependent behavior of dynamic and static properties of preheated to 650°C Westerly granite, which should be considered for microseismic fracture monitoring surveys, is presented in this paper. A thermally treated cylindrical Westerly granite specimen was compressed hydrostatically to 5 MPa and loaded axially to 415 kN until failure in a triaxial loading cell at the strain rate of 3.2 × 10-6 s-1. Longitudal wave (P-wave) velocities were measured periodically with triaxial ultrasonic system of transdusers along three orthogonal directions during loading time, until failure. Both dynamic (P-wave velocities along three orthogonal axes, and anisotropy of these velocities) and static (axial, lateral and volumetric strain) properties of the sample demonstrated significant variation with time (e.g., vertical P-wave velocity first increased by 58%, from 3100 m/s to 4900 m/s, and then dropped by 38%, down to 3048 m/s). Onset of fracture initiation occured at 0.5% of axial strain. During the initial stage, axial compaction prevailed in tested Westerly granite sample, inasmuch as closure of thermally generated cracks oriented horizontally was dominating. After axial strain reached 0.5%, the specimen lateral dilatancy was uncovered. Afterwards, opening of vertically oriented stress-induced fractures started to dominate, which had a response in both ultrasonic and mechanical data. It lead to presence of stress-induced anisotropy of the dynamic properties. As the velocity anisotropy, as well as the wave velocities, strongly vary with time and with increasing axial strain. At axial strain equal to 0.78% microscopic failure of the specimen was detected. For accurate localization of microseismic events during fracture monitoring a reliable time-dependent and anisotropic velocity model should be implemented.
Bazhenovskaya Suite of Severo-Demyanskoe Field: Multi Fracturing Well Completion – Story of Success
Authors: Sigarev Sergey , Kustaryov Dmitry , Prokhorov Alexey , Nikitin Pavel , Samoylov Mikhail , Koltypin Oleg
Published: October 2018

In recent years, the issue of the Bazhenov development as one of the main hard-to-recover oil reservoirs is getting more and more pressing for the Russian oil industry. Lack of knowledge about this reservoir underpins difficulties that arise both in hydrocarbons production and in well construction and completion. This paper presents a story of success in well construction with a multi-stage frac design in the Bazhenov Suite of the Severo-Demyanskoye Field (OOO RN-Uvatneftegaz). One of the distinctive features of this project is a wide use of the Russian domestic equipment and technologies.

It is not possible to obtain economic oil rates from the Bazhenov without additional flow stimulation. The selected stimulation method was multi-stage hydraulic fracturing with a considerable proppant mass (large-volume multi-stage fracturing). The average frac job was 80 tons of proppant each; the mixture pumping rate was 5.5 m3/min, thus making it possible to place the defined amount of proppant and create the expected fracture geometry.

To ensure accident-free drilling and well completion as well as to update the data needed for hydraulic fracturing, advanced preliminary geomechanical studies were carried out.

In order to maintain operability of the well equipment while waiting on frac jobs (over 8 months), Russian-made heavy potassium formate brine was used as a completion fluid for the first time in Russia.
Complete Assessment of Complex Unconventional Saudi Arabian Producer Using High Definition Spectral Noise Logging and Numerical Temperature Modeling
Authors: Oparin Maksim , Altayyar Tayyar , Al-Otaibi Nashi , Sheshtawy Mohamed , Yassin Maged , Frolov Alexander , Vorozhikhin Sergey
Published: October 2018

Unconventional hydrocarbon production has been known to revolutionize the oil and gas industry in the last decade. Though the advancement of drilling and well completions associated with tight sands and shale production, the assessment of downhole completion and fracture production remains challenging. The paper illustrates innovative approach to assess the success of multistage fracturing systems, evaluate both hydraulic and swellable packer condition, behind liner flow, and quantitative assessment of stages contribution.

The paper will discuss logging techniques using high definition spectral noise logging and numerical temperature modeling to assess flowing fractures, horizontal liner and behind liner well integrity including isolating packers and quantitative estimation of stage production in unconventional horizontal producer.

Downhole logging including a set of conventional multiphase sensors alongside with high precision temperature and high definition spectral noise logging was run in one of Saudi Aramco largest unconventional reservoirs to provide complete assessment of the horizontal section integrity and stage contribution.

The survey confirmed the success of fracturing process across the horizontal section and application of the new type of the completion.

Numerical temperature modeling was used to quantify flow across each production ports and at the top of each stage. The integration of all data set provides complete understating of well completion and production in one run. The quantitative assessment provided by numerical temperature simulation was in good correlation with the bore hole conventional array production logging results.

The results of the survey provided detailed assessment of the horizontal lateral production with high resolution across every producing port and provided valuable information about behind liner fracturing efficiency and completion packers’ integrity in one run.

Logging tools didn't include mechanical rotating parts, providing high degree of safety and reliability and leaving a very low foot print on the well. Comparison with array production logging run completed separately.
Fatigue Tracking for Mud Motors and MWDs in Unconventional Wells
Authors: Mills Kathleen , Menand Stephane , Dao Ngoc-Ha
Published: October 2018

As the industry continues to drill increasingly complex wells, the demand put on drilling equipment has increased and will continue to increase. Preventive maintenance often falls to the wayside in favor of keeping the same equipment operational for longer until a failure occurs, which can be very costly and potentially catastrophic to the equipment provider. Fatigue tracking makes it possible to predict failures ahead of time and prevent such incidents. However, the most commonly used fatigue tracking methods are based only on rotating hours and do not take the bending stress into account. Electronic drilling recorders (EDR) coupled with bottom hole assembly (BHA) models allow for better estimation of the fatigue performance by calculating the actual bending stress along each piece of equipment, such as the mud motor or measurement while drilling (MWD) tool, leading to a more reliable fatigue tracking method.

A case study of fatigue on a common motor and MWD over the drilling life of a well provides valuable information on how to monitor and react to different fatigue scenarios. By using an advanced stiff string model to calculate stress distribution along the motor or MWD coupled with standard fatigue prediction models, valuable information can be learned about the motor and MWD conditions.

One case that will be examined involves a typical well trajectory such as those drilled in the US land market today which involve a high dogleg curve to reach a target formation, with dog leg severity (DLS) locally reaching 18 (deg/100') generating high bending stress and thus fatigue. The consequence on fatigue life can be dramatic through the BHA for even just one exceptionally high dogleg. By using the continuous surveys taken by an MWD tool, to account for the actual tortuosity of the well, the potential fatigue becomes even more significant. Another decision that is commonly made without much regard for fatigue consequences is that of stabilizer placement along the BHA which can dramatically shift the distribution of bending moment and thus extend the life of a mud motor. Simulations will show how wellbore tortuosity can affect dramatically the fatigue life of mud motor and MWDs.

By illustrating several common examples of fatigue influencers, engineers will be better equipped to determine the impact of different decisions on the potential motor and BHA fatigue. Better understanding of the nature of fatigue and the consequences of larger bend motors, higher doglegs, and better surveying practices, for example, can lead to better decision making and the reduction of fatigue failures.