bluuebunny/crossref_metadata_2025 huggingface dataset:
3D Simulation of Low Salinity, Polymer, Conventional, Water-flooding & Combination IOR Methods – Heterogeneous & Varying Wetting Conditions
Authors: Aladasani Ahmad , Bai Baojun , Wu Yu-Shu , Okasha Qutaiba
Published: October 2015

In this paper a five spot well patterns is used to study Low Salinity, Polymer, Conventional, Water-flooding and the combination of Polymer flooding and LSWF. The aforementioned cases are applied under different wetting conditions. Oil recovery is a function of reservoir forces. Effective IOR implementation requires the proactive identification and contribution of the dominating reservoir forces, over the course of the field development. The work in this paper uses a validated, compositional simulator in addition to validated relative permeability and capillary formulations to simulate LSWF, PF, Conventional, Water-flooding and combination of PF + LSWF in a multi-dimensional, anisotropic and aerially heterogeneous model, under various wetting conditions. Wettability modification is also simulated using start and end relative permeability, captured and validated from literature.

The initial wetting state is an important criterion for LSWF. The incremental recovery in oil-wet systems, or "typical carbonate reservoirs," is more rapid and thus requires less dilution of the injected brine salinity. In addition, simulation results indicate substantial un-swept quantities of available oil saturation. Therefore, the role of polymer flooding is examined along with conventional water-flooding in wetting conditions where LSWF may not achieve significant incremental recovery. LSWF is not effective in intermediate wetting conditions and Polymer flooding yields higher recovery factors in all water wet conditions.

The impact of reservoir damage has an adverse effect on the development's recovery factor and polymer flooding yields the highest incremental recovery in case of low permeability formations. In oil wet conditions the performance of PF and LSWF is similar especially in weak oil wet systems due to the equal contribution of their respective displacement efficiencies. In strong oil-wet conditions the combination of PF + LSWF yields the highest recovery factor. The wetting conditions, formation heterogeneity and permeability magnitude all impact IOR selection and suggest that each oil reservoir has a unique ionic environment that changes naturally and by human intervention, therefore it is important to study different IOR methods at different stages of the field development.
Prediction Method of In-situ Stress in Non-isopachous Ultra-deep Composite Salt-gypsum Formation
Authors: Hou Bing , Chen Mian , Jin Yan , Diao Ce , Lin Botao , Lu Yunhu
Published: October 2015

Soft rocks, such as rock salt, claystone-gypsum, and gypsum, can cause tremendous dangers to wellbore wall surrounding rock deformation and damage. These rocks are the key to predict in-situ stress more accurately in ultra-deep composite salt-gypsum formation and ensure the safety of casing design after drilling or well completion. Therefore, a new method to predict in-situ stress in ultra-deep composite salt-gypsum formation needs to be established.

To date, existing in-situ stress experimental methods are unsuitable for salt-gypsum formation; these methods need in-situ stress data to design drilling and completion casing strength to ensure casing safety in salt-gypsum formation. To solve such problem, this study measured the in-situ stress of rock salt-gypsum for the first time by deformation rate analysis (DRA)–Kaiser method. Results showed that combining DRA and Kaiser methods can increase the credibility of the test data. When the stress–strain difference curve displays the inflection point and the stress–acoustic emission intensity curve has significantly increased point, the stress corresponding to the axial compression is the stress that the rock suffered. This stress avoids displaying several Kaiser points in previous Kaiser effect experiments.

Based on in-situ stress and actual tectonic evolution, a 3D multi-layer complex geological model was established. This model solves the problem wherein the previous model was oversimplified and could not truly reflect the actual geological structure during the simulation process. A numerical method of in-situ stress field for the entire regional composite salt-gypsum formation was developed based on the finite difference method and nonlinear prediction theory. This method solves the problem wherein laboratory experiments and theoretical calculations have difficulty in obtaining the in-situ stress of ultra-deep composite salt-gypsum formation.

According to the study results in this thesis, in-situ stress and casing integrity are evaluated in ultra-deep, high temperature, and high pressure composite salt-gypsum formation in Kuqa piedmont, Tarim Oilfield. Combined with actual situation, the rationality of in-situ stress predicting methods is verified in ultra-deep composite salt-gypsum formation.
Integrated Drilling Database Enables Automated Drilling Engineering Design
Authors: Shi Xiaoyan , Zhou Yingcao , Song Peng , Zhao Qing , Jiang Hongwei , Huo Zongqiang , Yang Guang , Zhai Xiaoqiang
Published: October 2015

As the rapid development of drilling techniques and data acquiring techniques, more and more drilling data are available. Storing, managing and effective using of these massive data are crucial to optimized drilling engineering design and strategic decision. This article is to research and design an integrated drilling database, and then further explore the innovative usage of the available drilling data. Based on the detail analysis of drilling database requirement, this article researched and designed drilling database by three phases: conceptual design, logical design and physical design. In the conceptual stage, the requirements of drilling design data, real-time drilling data and drilling construction data are extracted and analyzed, then E-R model is constructed. In the logical design stage, data tables and table relationship are designed and refined based on the E-R model. In the physical design stage, physical structure is selected for the logical data model to satisfy the application requirement. The designed drilling database is targeted data storage and management basis for drilling engineering design and craft software, real-time drilling software and drilling history management software; it conforms to drilling business process, contains comprehensive and detailed content and has high performance and refined data table structure. The construction of unified drilling database enables the efficient storage of mass drilling data and further data mining and analysis of drilling information. This work further researched the algorithms of automatic drilling engineering design, especially for automatic wellbore geometry design, based on the available data in the database. This article introduced a systematic method to design an integrated drilling database, which supports design data, real-time data and drilling management data. It also proposed an innovative way of drilling engineering design: automated drilling engineering design based on the data in the integrated drilling database and pre-installed rules.
Behaviour Intention Analysis Among Workers at Oil and Gas Company
Authors: Musa R. Abdullah , Fadhli Achmad , Kusminanti Yuni , Erwandi Dadan , Lestari Fatma
Published: October 2015

The study is purposed to obtain the intention of behaviour and contributing factors such as attitude, subjective norm (SN) and perceived behavioural control (PBC) as adopted from belief, attitude, intention and behaviour theory. Data collected through distribute the questionnaires among 436 workers from all levels, top management, middle managers and workers. The safe behaviour intention is 4,37 (index 5) and short cut behaviour (SCB) is 2,59 (index 5). The highest values from index would indicate the positive behaviour. Means beta are attitude 9.22 (index 25); SN 18.95 (index 25) and PBC 4.30 (index 5). It may be seen that the most contributing factor is PBC. The study concludes that the implementation of safe behaviour in the company is already good and influenced by external factors (PBC) rather than internal or individual factors (safety attitude). Safety behaviour intention may be improved by increasing the awareness, responsibility and HSE competency among workers. It should be supported by effective supervising and effective safety leadership in every level of management.
Synthesis and Evaluation of Gas-Wetting Alternation Agent for Liquid-Blocking Effect in Condensate Gas Reservoirs
Authors: Jin Jiafeng , Wang Yanling , Zuo Jiaqiang , Dai Caili , Wang Kun , Jiang Ling , Ren Jinheng , Ma Hanqing
Published: October 2015

Liquid condensation near wellbore region may kill gas production in gas-condensate reservoirs when pressure drops to lower than its dew point. One potential way to overcome this problem is to alter reservoir wettability to gas-wetting to reduce condensate accumulation in the near wellbore and maintain high productivity. It was believed that condensate accumulation can be removed by altering the wettability of reservoir from liquid-wetting to gas-wetting. The aim of this study was to investigate the effect of wettability alternation on condensate gas recovery efficiency in porous media.

Different molar ratios between fluorine-containing copolymer monomer and acrylic monomers were used to synthesize a gas-wetting alternation agent. Then Contact angle measurement and Owens two-liquid method were conducted in the laboratory, meanwhile, the effects of alternation agent concentration, salt concentration, pH and temperature on the gas-wetting core were evaluated.

Results showed that when the molar ratio of fluoropolymer monomer: acrylic acid was 1:2, the synthetic product could alter the wettability of core from liquid-wet to preferential gas-wetting. The contact angles of brine and oil can be altered from 23° and 0° to 137° and 90° by 1wt% FP-2 treatment, respectively, the surface free energy of core was improved from 67.52 to 1.66mN/m, the wettability of core was altered into in neutral gas wetting. And the treated cores can keep neutral gas-wetting within a condition of 100000mg/L, 120°C, pH=5~7. This novel gas-wetting alternation agent can be used to solve the problem of liquid blocking effect in gas condensate reservoirs and thus improve gas recovery.
Indonesia's Top 7 Energy Issues: Focusing on What Really Matters
Authors: Saputra Edi
Published: October 2015

The Indonesian government faces numerous challenges. Given the government's resources are limited, it is important to focus on the essential ones, prioritising the crucial issues over the incidental ones, the urgent initiatives over the trivial matters.

Identifying the key issues will enable the government to put the right focus in the right places, to mobilise the people, resources and finances in the right direction. In the light of this, this paper identifies seven key energy issues which should be given the highest priority by the government and other relevant stakeholders.
An Integrated Method for Remaining Oil Prediction Based On Time Lapse Seismic Inversion and its Application
Authors: Linggao Li , Lideng Gan , Zhangxin Zhangxin , Wenhui Du
Published: October 2015

An integrated solution is presented to take good advantage of time lapse seismic data and reservoir simulation results to delineate the potential area of remaining oil. First, a coupled time-lapse AVO inversion method is presented and applied to a test area of time-lapse seismic project in DQ oilfield and resulted in two vintages of elastic properties for each survey. Second, volumes of a direct hydrocarbon indicator (DHI) are calculated from each vintage of elastic properties. An empirical equation of relative DHI variation with remaining oil reserves is obtained. Such empirical equation is then used to predict the change of remaining oil between two acquisitions. At last, the predicted remaining oil change and remaining oil of base survey from numerical simulation is used to circle the potential area of residual oil.
New Nano-Geopolymer Cement System Improves Wellbore Integrity Upon Acidizing Job: Experimental Findings
Authors: Ridha Syahrir , Yerikania Utami
Published: October 2015

Acid stimulation job is one of alternative technique used to improve well productivity. However, improper usage and design of this method may pose problems to the cements surrounding the perforation area of the well and it may lead to well integrity problems. Therefore a good the cement system must exhibit the physical and chemical properties that are not reactive to most types of acids used in acidizing job. This paper developed a new nano-geopolymer cement containing portions of nano-scales of silica, flyash and alkaline liquid under geopolimerization process.

The experimental work is simulated under downhole conditions at pressure up to 4000 psi and temperature up to 120°C. Strength buildup profile was analyzed using Ultrasonic Cement Analyzer. This research also exposed cement samples into acidic environment of mixed HCL and HF with the ratio of 12% and 3% up to 24 hours. Curing times conditioned to be varied along the test to better describe the chemical and mechanical changing due to acid. Advanced Scanning Electron Microscopy (SEM) is used to describe microstructure deformartions of cement samples.

Compared to class G cement, pure geopolymer and nano-SiO2 geopolymer cement have better acid resistance as they experienced less strength loss. It is found that nano-SiO2 possessed the tendency on enhancing pure geopolymer cement property through the strength test. Although the strength degraded, the strength loss is not as much as class G and high initial strength value of nano-SiO2 geopolymer cement gives benefit in maintaining high strength value after acidizing. Sample NG1 with 1% nano-SiO2 obtained the highest strength value and minor crack after 24 hours acid exposure.

The result shows that the new cement system can improve the wellbore integrity by resistingacid alteration and penetration upon acidizing job. At the same time the CO2 emissions from producing conventional API cement can be eliminated by the new nano-geopolymer cement.
Indonesia Wellwork Performance Management and Evaluation
Authors: Prasetya Afriandi Eka , Herputra Shanni Ardhana
Published: October 2015

There are 63 work areas in Indonesia producing 800,000 barrels of oil per day. Workover and well service or wellwork activities are carried out by PSC Contractors as one of backbone activities which compensates production decline. As a state institution for upstream petroleum activities in Indonesia, SKK Migas is responsible to manage and evaluate the performance of wellwork activities to serve the purpose of maintaining national production.

More than 31,000 wellwork activities are performed annually and contribute to the production of more than 40,000 bopd. 2015 program is at 36,000 activities to contribute production target of 50,000 bopd. All wellwork activities are reported to SKK Migas by the PSC contractors in the form of a spreadsheet. SKK Migas evaluates the wellwork performance to be used as consideration in wellwok program approval for the following year. The evaluation includes numbers and types of activities, time and cost, and the contribution to production.

During 2013 and 2014, SKK Migas managed to collect reports from PSC Contractors which consists of more than 60,000 wellwork activities. Based on the evaluation, SKK Migas also give appreciation to the PSC contractor who has the best performance on wellwork activities.

This paper will illustrate how SKK Migas manages large scale wellwork activities in Indonesia using spreadsheet. This paper also illustrate how historical performance is compared, evaluated and analyzed for forward planning of wellwork activities.
Successful Application of Unique High-Density Water-Based Drilling Fluid Used in Zhaotong Shale Gas Horizontal Wells
Authors: Yan Lili , Li Congjun , Zhang Zhilei , Wang Jianhua , Xu Xianguang , Sun Jinsheng , Su Yinao
Published: October 2015

Shale-gas plays have gained significant importance in China. Sichuan Basin, industry's primary focus for shale gas, has finished hundreds of wells. The employed drilling fluids for drilling shale horizontal wells here are mostly oil-based muds (OBMs), due to its well-known excellent performance and the considerable geologic structural complexity. With the implementation of new national environmental law, the application of OBMs will be limited. A pressing goal is to develop a high-performance and environmental-friendly water-based mud.

This paper discussed the research and application of a novel high-performance water-based mud for shale gas horizontal wells in Zhaotong area of Sichuan Basin. The morphology, mineralogical composition, Porosity and cation exchange capacity of the shale samples, and the key technical problems in the target formation were first analyzed. Then, a novel hybrid silicon shale inhibitor, rigid nano-polymer plugging agent, liquid filtrate loss control agent and liquid lubricator were prepared, respectively. Incorporated with other selected agents, an innovative water-based drilling fluid (HPWBD) with a density of 2.2 g/cm3 was formulated and applied.

Extensive lab work was carried out to compare the properties of HPWBD with field oil-based drilling fluid. The results show that HPWBD had excellent inhibitive and lubricant properties, closing to the oil-based drilling fluid. Besides, HPWBD was highly plugging and rheology stable after rolling at 100 oC under high density conditions. Then, the HPWBD was applied successfully in Huangjinba YS108H4 well. The drilled horizontal well interval reached a length of about 1500 m. During drilling, no downhole troubles were observed, no bit balling was found, the borehole diameter was regular, and the electrical logging operation was successful just at the first time. Meanwhile, it reduced cost and environmental concerns associated with cuttings transportation and disposal.

In a word, the developed high-density water-based drilling fluid showed outstanding performances, closed to oil-based muds. Moreover, it was beneficial to the environment and could reduce the cost significantly. It will provide an alternative to oil-based mud for safe and environmental development of shale gas in China.
Shifting the Paradigm: ESP with Induction and Permanent Magnet Motor Application in Low Productivity and High GLR Wells
Authors: Dwitiya Dipta , Hamzah Kamal , Prakoso Noke Fajar
Published: October 2015

With the imminent decline in gas availability for continuous gas lift operations, Kaji Field, Rimau Block, south Sumatra, Indonesia needed a new lifting method to replace gas lift utilized in marginal wells which produce from Telisa formation (sandstone). This project aimed to evaluate the applicability of electrical submersible pumps (ESP) in wells that are not commonly produced with ESP, and was divided into two phases. The first saw the implementation of an existing ESP with several completion modifications, and the second involved a trial of ESP with the permanent magnet motor system (ESP PMM), which at the time of implementation was a newly applied technology in Indonesia.

The alternative artificial lift (AL) configuration had to be operable in wells with low productivity (Productivity Index less than 1 bbl/psi) and have excellent gas handling capabilities (GLR above 3,000 scf/bbl). This presented a stern challenge for the application of submersible pumps due to their basic nature of operating in high liquid rates. Therefore change management also became a crucial agenda in the project. Furthermore, the technology had to be more energy efficient because power generation was also an issue related to the decline in the availability of gas for fueling Kaji's power plants.

The first phase saw the installation of the first ESP unit equipped with an induction motor. The low influx and gassy condition of the well was mitigated by setting the pump below perforation to improve pump submergence. A shroud was also utilized to support natural separation of gas before entering the pump intake, and it also helped in creating fluid velocity to provide the motor with sufficient cooling effect. This configuration resulted in excellent productivity within its first one hundred days of production, providing a cumulative oil production equal to twice the amount when produced using gas lift, i.e. from 3,983 to 7,999 barrels of oil within the same time duration. The second phase of the project saw a similar completion strategy in a further two wells, this time with ESP PMM. The result was continuous and safe production, providing a production gain of almost 100 BOPD from the two wells, and with a 100% increase in energy efficiency.

This effort has proven ESP's applicability in low influx and high GLR wells, and most importantly has prevented production loss caused by forced shutins from gas lift insufficiency. This provided valuable information for further decisions regarding installations and configurations of artificial lift in Kaji Field and other similar fields, and has allowed us to make the decision to progress further with the transition from gas lift to ESP as the main artificial lift of the field, ultimately supporting the effort to sustain production.
Geomechanics Improves Drilling Operations and Reduces Non-Productive Times (NPT) in Kilo Field, Offshore Northwest Java
Authors: Ong See Hong , Power William L. , Sitio Aprianto , Tanjung Erwindo
Published: October 2015

Recent drilling of moderately to highly deviated development wells in the Kilo Field has proven to be extremely challenging. Numerous lost-time incidents including stuck pipe, pack-off, and difficulties in running casing were experienced, particularly when drilling through the Main-Massive Formation. Earlier analyses pointed to mud material quality issues, but drilling performance benchmarking with other nearby fields ruled out this explanation. Faced with continually high NPTs, a geomechanical study was initiated to mitigate the wellbore instability problems. The recommendations arising from the comprehensive geomechanical and drilling experience analyses have been implemented to improve performance during subsequent development drilling.

The field-wide geomechanical model indicates the Kilo Field is characterized by a state of stress that is transitional between a normal and strike-slip faulting regimes. The combination of relatively large differential stress and relatively weak rocks means the field is potentially subject to stress-induced wellbore instability problems. However, observations of numerous time-dependent failures imply secondary influences must also be considered to arrive at possible remediation strategies. A systematic ranking process has been developed to delineate the primary causal mechanism of wellbore instability. This process suggests that the major contributor to the time-dependent deterioration process is rising pore pressure caused by the invasion of drilling fluid into micro-fractured formations, and then exacerbated by less-than-optimal drilling practices. This finding, together with the improved geomechanical understanding of the Kilo Field, provides the basis for optimizing mud weights and wellbore trajectories as well as formulating appropriate drilling strategies to maintain the mud hydrostatic support (overbalance) in future drilling. The finding also highlights the importance of integrating geomechanics with drilling practices when developing strategies to mitigate unstable hole problems.

This paper presents a comprehensive, ordered workflow that integrates the disparate data available in a mature field to identify the most likely causative mechanisms of the time-delayed wellbore instabilities. This knowledge was then used to develop strategies for optimizing future drilling operations in the Kilo Field.
Wax Deposition Study in a Cold-finger System with Model Oil
Authors: Fan Kaifeng , Huang Qiyu , Li Si , Zhao Dan
Published: October 2015

Wax deposition problem occurred during crude oil production and transportation process is a hot one and has brought huge economy losses around the world. This paper focused on the mass and heat transfer process during wax deposition with cold-finger experiments by method of differential scanning calorimetry (DSC) and gas chromatography (GC). Two sets of experiments with 15 °C and 20 °C temperature difference were conducted using the model oil with wax content of 10 wt. % for 120 h. During each experiment, the wax-solvent mixtures at two radial positions of two horizontal planes and deposits are sampled for DSC and GC analysis.

The dissolved wax content gradient of the wax-solvent mixture at the same height is from the tank wall to the cold-finger, which is just opposite of its temperature gradient. As the diffusion proceeds, the total proportion of wax with carbon numbers of nC21~nC39 gradually decreases near the tank wall, but increases near the cold-finger. Furthermore, compared with the initial wax-solvent sample, the absolute mass ratios of wax molecules heavier than nC31 become greater in the deposits under 15 °C and 20 °C temperature difference, while the mass ratios of those lighter than nC32 decrease. This variation trend indicates that under this cold-finger temperature, heavy wax molecules continually diffuse into the deposition layer and meanwhile light wax molecules are displaced out of the deposition layer. The nC32 is the critical carbon number (here we defined the carbon number from which can deposite on the cold-finger as the critical carbon number) heavier than which the wax molecules can deposit in this condition.

This paper intensely analyzed the wax molecule distribution conditions from the view of heat transfer and mass transfer theories. It will undoubtedly promote the investigation of wax deposition mechanisms of waxy crude oil.
Application of Cellulose Nanofiber as Environment-Friendly Polymer for Oil Development
Authors: Kusanagi K. , Murata S. , Goi Y. , Sabi M. , Zinno K. , Kato Y. , Togashi N. , Matsuoka T. , Liang Y.
Published: October 2015

Cellulose nanofiber (CNF) is a biodegradable material. It can be obtained from natural cellulose through simple process; TEMPO oxidation. Its suspension in water shows high viscosity by the entanglement of fibers each other, owing to its high aspect ratio and the balance of electrical repulsion and hydrogen bond between fibers. In addition, it can regain its viscosity after shearing, which seems to be efficient polymer for E&P industry. In this study, we conducted the next core flooding experiments; polymer flooding and profile modification, and evaluated the applicability of CNF as environment-friendly polymer for EOR process. For the polymer flooding, Berea sandstone core of 145 mm in length and 1 inch in diameter was first prepared to be the residual oil saturated condition by the enough volume of water flooding with the API brine. After that, the 0.1 wt% CNF suspension was injected. As a result, additional oil was recovered, but the differential pressure between inlet and outlet of the core reached 5 MPa when 0.9 PV of the CNF suspension was injected. For the profile modification, we introduced high permeability column of 16 mm in diameter along the center of the sandstone core axis by packing and sintering glass beads. First, the core was saturated by the oil and the primary water flooding with the API brine from upstream was carried out until no more oil was recovered. Second, pure water for pre-flash, the 0.4 wt% CNF suspension and cross-linker solution of AlCl3 were injected successively from downstream for gel blocking inside high permeability zone. After the gel treatment, the secondary water flooding was carried out, and it improved oil recovery from 13.3 % to 24.3 %.

We could confirm the ability of CNF suspension to control mobility owing to its viscosity, and to make bypass in low permeability zone by blocking up easy channel when cross-linked with aluminum ion. However, we got the results that the CNF suspension shows poor injectivity because filtration occurs in the sandstone core during injection.
Experimental Investigation of Crude Oil Emulsion Physicochemical Properties and Demulsifier Dosage Prediction
Authors: Alomair Osamah , Alqabandi Salman , Malallah Mariam , Alajmi Amer
Published: October 2015

One of the common methods of reducing or eliminating the emulsion is the use of different chemical demulsifiers depending on the type of crude oil and water cut. This method is widely used in Kuwait Oil Company (KOC) at wellheads and gathering centers (GC). However, some wells have practice increases of demulsifier dosage as a result of increase in water content. Consequentiality, KOC initiated a program for optimization of chemical consumption for water/oil emulsion separation in the surface facilities at West Kuwait. As a result, of one year oil field statistical analysis of crude oil emulsion collected data. The results indicate that there are four oil wells of a different physical property could be very helpful for our study. Such properties include emulsion viscosity, size of water droplets, surface active materials, resin to asphaltene ratio (R/As), emulsion temperature. Over and above the demulsifier efficiency and dosages were evaluating using the calculated emulsion separation index (ESI) and interfacial tension measurement. As a result the oil field laboratory test indicates that the viscosity of emulsion increases to at least from 12 to17% of its original value based on dry condition. The average droplet size distribution near to (1–10) μm was highly effect on emulsion stability. Moreover the emulsion behavior was linked closely to the film form around the water droplets that are believed to result from the adsorption of high-molecular-weight polar molecules (asphaltene) and fine inorganic solids. There surface-active behavior that makes them good emulsifiers. Also it was found there are a consistent relationship between emulsion stability and relative resin to asphaltene content R/As for all four of the field samples under study. The crude oil of high emulsified water, near 30%, contains low (R/As, 0.84). However, as resins to asphaltene ratio increased the emulsion become unstable and emulsified water decrease up 9 %. This relationship could be used as the method to indicate the more likely oil field areas of strong emulsions and the suitable practical methods for treatment. Also from the well head operating conditions collected data; emulsion temperature, well head pressure, salinity of emulsified water and IFT. From the laboratory bottle test and oilfield crude oil emulsions data. The demulsifiers dosage was predicted using the proposed empirical model. In addition it could be used as a good tool for the new or the incumbent demulsifier evaluation.
A Self-Adaptive Surrogate-Assisted Evolutionary Algorithm for Well Placement Optimization Problems
Authors: Sayyafzadeh Mohammad
Published: October 2015

Finding an optimal well placement scenario is a complex and computationally intensive problem. The major computational cost is associated with the numerical reservoir simulation which should be executed for the fitness evaluation of each scenario. For such problems, a robust optimization algorithm is required. Population-based algorithms are powerful, but computationally demanding, optimizers. Surrogate-assisted algorithms have been developed to reduce the CPU-time of these optimizers, by substituting the original fitness function (OF), partially or completely, with an approximation function (AF), often known as proxy or surrogate.

in these algorithms, a model management strategy should be implemented to use the OF effectively and minimally, during the optimization process, fn this study, a self-adaptive model management strategy is developed, in which two surrogates are required. The first surrogate approximates the fitness function landscape, and the second one estimates the fidelity of the first surrogate over the search space (uncertainty map). According to the estimated uncertainty, the probability of using the OF is calculated for each individual, and then the algorithm stochastically decides to use the OF or AF. A heuristic fuzzy rule is applied to define the range of probability values in each evolution-cycle, based on the average fidelity of the second surrogate. The proposed technique is installed on a genetic algorithm, and two artificial neural networks are used as the proxies, which are trained online.

The robustness of the proposed algorithm is analyzed using a semi-synthetic reservoir model, PUNQ-S3. The outcomes are compared with the results achieved by two common algorithms, a typical (unassisted) genetic algorithm, and an offline-learning surrogate-assisted genetic algorithm. The comparison indicates that the proposed method can reduce the computational costs up to 48%. This surrogate-assisted algorithm may enhance the applicability of population-based algorithms in well placement optimization problems, by reducing the associated computational costs.
Advances in Mooring Integrity Management
Authors: Wales Stuart , Lee Tim , Carra Chris , Potts Andrew E.
Published: October 2015

Mooring Integrity Management has gained much interest in recent years as the failure rate for FPS mooring systems has been found to be significantly higher than expected. Existing mooring integrity management practices have not provided adequate protection against such failures. This paper provides an overview of recent advancements in the understanding of fundamental degradation mechanisms applicable to mooring systems and improvements to mooring system integrity.

Advancements in the understanding of mooring system degradation mechanisms will be explored through reviews of recent Joint Industry Projects (JIPs) that have looked at corrosion mechanisms for chain and wire rope, as well as remaining life assessment for corroded chain links. Recent advances in understanding of wire rope birdcage formation and degredation will also be presented.

Improvements to the approaches to management of mooring integrity will be provided by an overview of the DeepStar® supported industry study that has developed Model Guidelines for Mooring Integrity Management (MIM) for permanent mooring systems (AMOG, 2013). These Model Guidelines serve as the foundation for future implementation of risk-based inspection planning for mooring systems. The framework for a risk-based inspection program can be used by the operator to meet the risk profile of the individual facility as well as corporate and regulatory guidelines. The guidelines identify the required practices at each stage of the mooring system life cycle in order to minimize the risk of degradation mechanisms arising from design, construction, installation and operations practices.

Fundamental to the reliability of this methodology are the means to estimate the long-term degradation processes, such as corrosion, wear, fatigue and constructional disturbance, and the commensurate reduction in residual strength capacity and degraded fatigue endurance. The former of these aspects has been the subject of two JIPs, which have advanced the understanding of corrosion and wear processes (SCORCH JIP) and the commensurate reduction in strength and fatigue endurance (Chain FEARS JIP). The latter, constructional disturbance, is the subject of a proposed JIP, leveraging observations of degredation with numerical techniques.

This paper summarizes significant contributions to the understanding of the key causes of mooring component degradation and improved techniques for the effective management of mooring system integrity.
A Case Study on the Successful Application of Solids Lubricants in Directional and Horizontal Drilling Operations to Reduce Torque and Drag and Improve ROP in One of the Carbonate Oil Reservoirs
Authors: Mohammadi Mojtaba Kalhor , Nowtarki Koroush Tahmasbi
Published: October 2015

Current advancements for the development of oil and gas reservoirs require drilling directional and horizontal wells. Besides the technology for drilling directional and horizontal intervals, drilling fluids play an important role to reach the target. Conventionally, liquid lubricants including mineral and vegetable types have been used to reduce the torque and drag during directional drilling. As the result, high torque and drag was observed during drilling in rotation and sliding mode. This limits required sliding from plan and decrease ROP with the possibility of stuck pipe.

This paper reviews the application and the use of different types of solids lubricants in drilling fluids during drilling directional and horizontal intervals as an operational experience. Drilling fluids rheological properties were monitored and the effects of applying these solids lubricants was the reduction of torque and drag values. In addition, lubricity factor of the filter cake has been measured during drilling by using a lubricity meter to be kept in the proper range by changing the type and concentration of solids lubricants in the drilling fluids. All the data including torque, drag, lubricity factor, solids lubricants concentrations and ROP have been recorded versus depth to benchmark drilling performance.

Finally, application of different types of solids lubricants have been approved and showed ROP improvement especially during sliding mode in hard carbonate rocks in the reservoir. No stuck pipe has been recorded during the drilling of horizontal sections. In addition, liners were run successfully without any problem to the target.
Aquifer Deep Diversion Agent for Deep Reservoir Conformance Control
Authors: Meng Xianxing , Haron Raja Noorlyana , Li Mingyuan , Maarop Nurisman , Lin Meiqin , Yang Zhihao
Published: October 2015

Premature water encroachment or early water breakthrough is a common problem in the industry. Ever increasing water cut will reduce oil recovery, decrease well's productivity and increase the cost of produced water handling. Conventionally the only solution to tackle aquifer dominant encroachment is to introduce a water shut-off chemical in the producer to stop water from coming in. However this solution has its own limitations and tackles the problem via zonal isolation that can also be achieved mechanically in many cases. In this paper a novel deep reservoir conformance control technology for aquifer is studied. The main characteristic of the chemical used in this technology is its ability to propagate deep into the reservoir for effective constriction and diversion of aquifer channels without the risk of near wellbore blockage. Aquifer Deep Diversion Agent (ADDA) is a form of solution with viscosity similar to water and is only soluble in the water phase. It aggregates once it contacts with high salinity aquifer water and is absorbed on water wet rock to form a microscopic constriction which creates diversion. Its strong adsorption on the rock surface will ensure strong and stable constriction. Its fail safe mechanism includes its inability to absorb on oil wet rock and it does not aggregate when it contacts with oil thus it will not impair the performance of oil bearing zones and the oil inflow performance. ADDA is readily mixed with water and, due to its similar viscosity to water, it has the same mobility as water that enables it to flow easily in the reservoir. Subsequently ADDA which is predesigned to trigger at a certain salinity and ion content and will only flocculate when it meets with saline aquifer water with the properties specific to the targeted reservoir to constrict the water path. Consequently, the aquifer water will be diverted into lower permeability zones resulting in an increase in mobilization of bypassed oil and a decrease of water cut. Unlike other technologies, ADDA is tailored according to the reservoir properties and particularly aquifer salinity. The size of molecular aggregation and its rate of aggregation can be designed in the lab based on specific ion composition in aquifer water.
Development and Application of Continuously Mixing Seawater-Based Fracturing Fluid System
Authors: Gao Ying , Shi Yang , Zhou Fujian , Xu Minjie , Yang Xianyou , Xiong Chunming , Han Xiuling
Published: October 2015

The fracturing operation on offshore-platform is limited by high transportation cost of fracturing equipments and other materials, load capacity of platform and other aspects. To overcome these difficulties, a seawater-based fracturing fluid system is developed, which can realize continuously mixing operation on offshore-platform. There are several characteristics for this fracturing fluid system: ① The most commonly used hydroxypropyl guar gum (HPG) is taken as a thickener, and this system is characterized by mature technique and wide application. ② Chelating agent is needless for this fracturing fluid system, so cost will be reduced greatly. ③ Instant dissolving of thickener is achieved through adding instant additive to realize continuous-mixing. ④ Cross-linking technique of seawater-based fracturing fluid is developed: a weak-alkaline pH-buffer SC-150 for seawater mixing and the matching multipoint organic boron - zirconium composite crosslinker GM-7010 are developed. This fracturing fluid system with better temperature-resistance and shear-resistance can meet general requirements of water-base gel fracturing fluid.

This seawater-based fracturing fluid system is featured by instant dissolving, easy preparation, etc., which has been successfully applied in the fracturing operation of low-permeability offshore reservoir in South China Sea. The pilot well was shut-in because of no production before fracturing treatment. 770m3 fracturing fluid 74m3 proppant are successfully injected during fracturing operation, and 20m3/d stable production is obtained after treatment.
Transient Flow Behavior of Horizontal Wells, Pressure Drawdown, and Buildup Analysis
Authors: Odeh A. S. , Babu D. K.
Published: October 2015

Four flow periods may occur during the transient behavior of a horizontal well. Drawdown and buildup equations describing the flow behavior of each of the four flow periods are given. Methods for analyzing data obtained from testing the well to determine permeability anisotropy in the drainage volume of the well, as well as the skin factor, are presented. The calculation procedures are illustrated by examples.
Experiences with Pumping Well Testing
Authors: Kabir C. S.
Published: October 2015

This work embodies our recent experiences with pumping well testing using the acoustic method. Three areas of testing are examined here: first, computation of changing liquid density throughout the liquid column at every time step; second, interpretation of the test using simultaneous downhole pressure and flow-rate data; third, static and dynamic response of the acoustic device.

An algorithm is developed to incorporate the gas/oil mass transfer effect (solubility) so that accurate gas velocity and in turn improved liquid density in the annulus can be computed. The effect of gas solubility is to reduce the gas volume and hence the total downhole volumetric flow-rate (BHF), without affecting bottomhole pressure (BHP) significantly. Transient interpretation improves when the gas solubility is accounted for.

A review of some of the wellbore hydrodynamic models and correlations is attempted in this study. The Godbey-Dimon hydrodynamic model is modified to simulate the moving liquid-column during a buildup test.

Transient interpretation of many field tests indicates that long-duration wellbore storage is the dominant feature in all cases. In general, the use of BHF together with BHP aids early-time interpretation. However, in pumping wells, complexity in well/reservoir flow and uncertainty in early-time-rate estimation do not allow the benefit of such analysis in every situation. Hence the need arises for long shut-in times in many cases. Nonetheless, the examples show that the acoustic method does produce interpretable quality data.

Field examples are used to examine both the static (accuracy) and dynamic response (resolution) of the acoustic device. The available literature suggests that the acoustic method can faithfully reproduce the absolute static bottomhole gauge pressure. This study shows that the results from dynamic tests (buildup) compare very favorably with those from downhole measurements.
Single-Trip Tubing-Conveyed-Perforating, Production Testing, and Pressure Buildup Testing in Nonflowing Wells
Authors: Barnes J. A. , Swafford C. V. , Snider P. M.
Published: October 2015

Procedures and tools have been recently developed to perforate, obtain a flow test, and record a downhole shut-in pressure buildup in oil wells which are not able of flowing to surface. For these tests, tubing conveyed perforating guns, downhole recording pressure gauges, and a hydraulic jet pump assembly with a specially designed blanking sleeve are run in the well. The well is perforated underbalanced and subsequently allowed to clean up by flowing until it dies. The blanking sleeve is then hydraulically shifted open, and the well is tested for an extended period using reverse flow jet pump lift. After completing the flow test, a pressure buildup with a downhole shut-in is acquired. The perforating, flow testing, and buildup are all obtained on a single trip with the workstring. Some advantages of the system are:

Accurate flow rates and water cuts are determined prior to completing the well. Multiple trips with the workstring are not required and rig time requirements are minimized. The well is not killed between perforating and flow testing. All equipment and operations are pressure actuated, eliminating the risks and costs associated with wireline operations. The bottomhole shut-in provides high quality information to evaluate additional stimulation benefits.
Managers' Strategic Reporting Judgments in Audit Negotiations
Authors: Brown-Liburd Helen , Wright Arnold M. , Zamora Valentina L.
Published: October 2015

Prior research has largely characterized audit negotiations as a dyadic relationship between auditors and managers. However, the Sarbanes-Oxley Act (SOX) substantially enhances the audit committee's oversight responsibilities for the financial reporting and auditing processes. Thus, negotiations post-SOX may be viewed as a triadic relationship that now involves the audit committee with the authority to scrutinize audit negotiations. Consistent with auditors considering their relative bargaining power and expectations of counterpart behavior, Brown-Liburd and Wright (2011) find that auditors are most contending when the audit committee is strong and the past relationship is contentious. We extend Brown-Liburd and Wright (2011) by examining the joint effects of these factors on managers' pre-negotiation judgments. We posit that rather than mirror auditor behavior, managers make different judgments because they have a different perspective and set of incentives than do auditors. Prior research suggests that managers are more flexible, more accurately determine their counterpart's goals and limits, and are more likely to use certain negotiation tactics than auditors. Further, managers have incentives to maximize the current outcome while maintaining their firm's reporting reputation. As such, managers will be less aggressive in responding to a contentious past auditor relationship, particularly in the presence of a strong audit committee that may ask difficult questions and potentially intervene against their favor. However, managers will act more aggressively to capitalize on a cooperative past auditor relationship, particularly in the presence of a weak audit committee that is passive or persuadable. To examine these two boundary conditions, we conduct an experiment with 137 experienced CFO/controllers. We find strong evidence supporting our expectations that managers act as if both the audit committee and the auditor jointly play important roles in ensuring high financial reporting quality.

JEL Classifications: M41; M42.