bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of Reduced Order Modelling Techniques for Downhole Logging Sensor Design
Authors: Zhang Qiong , Mendez Freddy , Longo John , Gade Sandeep , Peyaud Jean
Published: October 2015

Spectral gamma ray tools provide insights into the mineral composition of formations and such data can be used to distinguish important features of the formation around the wellbore. However, it is a challenge in cased-hole cases to anticipate the attenuation effects of casing within various conditions of density and thickness in an efficient manner. In this work, an innovative reduced- order Monte Carlo modelling technique is presented for cased-hole environment spectrum analysis and, specifically, to numerically determine the attenuation effects of gamma ray transmission through different materials. The presented computational method is developed accounting for different casing and cement thicknesses, and sensor positions within the borehole.

The reduced order model construction could be considered one level up from the regular Monte Carlo modelling procedure as it reduces the dimensionality induced by various parameters and therefore proves an extremely useful tool handling large-scale problems that are very common in complicated downhole environment. The adjusted source distributions are then utilized to generate and validate spectra to be applied for difference logging scenarios. Two exemplary field cases are presented: 1. An open-hole logged well; 2. The same set-up well but with steel casing.

The reduced modelling techniques are applied to the both cases and the possible impacts of different variable. e.g. borehole size, mud weight and cement thickness on the sensor-obtained spectra are discussed. Future work will involve a series of case studies .e.g. the sensitivity assessment of formation impurities and an extension of the Monte Carlo computed elemental standards to a great variety of nuclear downhole sensor designs.
Identification of Borehole Breakout Formation and Estimation of Stress Direction and Regime Using LWD Ultrasonic Caliper Measurements: A Unique, Systematic, and Real-Time Methodology
Authors: Khoo C. Y. , Gland N. F. , Lee S. S. , Ng H.. , Wong F. K. , Za'ba M. A.
Published: October 2015

Wellbore instability remains a leading threat to oil operators as one of the main causes of non-productive time worldwide. As drilling technology advances, logging-while-drilling (LWD) measurements contribute valuable information to help identify instability problems in real time. One of the important measurements is the LWD ultrasonic caliper measurement, which makes it possible to identify borehole washout, breakout, keyseating, and spiral-hole conditions. Having this measurement enables diagnosis of wellbore stability problems while drilling without the need for an additional logging run, which is especially critical in an unstable wellbore.

In the industry, breakout identification using image data can be a significantly user-dependent process and requires appropriate skills. The process is time consuming, and the final result can still be subjective. Further complication comes when considering a highly deviated well path or when the field stress regime is abnormal. As a consequence, drillers face difficulties using the LWD ultrasonic caliper data directly for wellbore stability diagnosis. We propose a methodology to overcome the limitation of conventional method and produce reliable quantitative breakout data to be used in real time, in an automated, systematic, and consistent way.

An engineering-based workflow is introduced to distinguish zones of stress-induced breakouts from other borehole enlargement types with improved consistency and which can be easily translated into programming language. Instead of image data, this solution uses sector data to extract the borehole shape information using the cubic spline method. Six stringent LWD ultrasonic caliper-specific breakout criteria are introduced and used to identify breakout intervals from the borehole shape data.

Adopting the idea from the World Stress Map (WSM) project, a data quality ranking was also performed using the result of the workflow. The quality ranking criteria (defined by WSM project) segregate the breakout results into five categories to infer the reliability of the breakout intervals identified. This quality ranking procedure will greatly improve the reliability of the output data in the workflow prior to quantitative usage. The result of the breakout identification is then used to determine the principle stress direction and the stress regime, using a 3D stress analysis method for deviated wells.
An Improved Approach to Simulate Low-permeability Fractured Reservoirs with Dynamic Hybrid Dual-Porosity Model
Authors: Shuhong Wu , Tianyi Fan , Xiaozhou Zhang , Hua Li , Qiaoyun Li , Xiaobo Li , Baohua Wang
Published: October 2015

It is a challenging work to simulate fractured reservoir from reservoir description stand point, especially low-permeability reservoir with natural/artificial and water-injection-induced fractures. This type of reservoir has been idealized by a set of disconnected matrix blocks within a network of connected fractures such as Dual Porosity model. It is assumed that fracture network is primary continuum for fluid flow, the matrix of low permeability, high storativity is considered to be a sink/source to the fracture. The matrix and the fracture communicate through an exchange term which describes fluid flow between matrix and fracture. It is assumed that the fracture system is in a steady state which does not change during production history.

In the development process of low-permeability reservoir with fractures, some phenomena arose different from the above assumptions. Water injection with high injection pressure will induce new fractures. The distribution of natural/artificial fractures will be complicated. The fractures would be open, get bigger in width/length or closed during the production with the variation of reservoir pressure. The above type of fractured systems could usually experience some abnormal phenomena such as high injection pressure in injectors but low pressure in producers at early stage while serious water channeling and high watercut at the medium stage of development. It is difficult to explain these phenomena by existing principles.

A dynamic hybrid dual-porosity model is presented for the serious water-channeling phenomena in the fractured low-permeability reservoirs in which dynamic fracture model and psudo-tenser permeability model are overlapped to Dual Porosity model. The fracture network is considered to be in unsteady state in which fracture has possibility to widen, lengthen, close during oil production. A K-tensor is introduced to describe these processes, which is a function of pressure, stress, density of fractures. The paper will detail dynamic hybrid model such as its assumptions, equations, mechanisms and also its applications in low-permeability fractured reservoirs simulation such as in Changqing and Jilin Oilfield.
Challenges in Modeling of High Clay Volume Gas Reservoir with No Water Production
Authors: Ezabadi Mehdi Ghane , Ramli Anis Salwa , Ataei Abdolrahim , Othman Tg Rasidi
Published: October 2015

The characterization of high clay volume reservoirs is a challenge in terms of cut-offs determination, saturation modeling, and simulation setup. These can be even more complicated when it incorporates zero water production from the transition zone. In transition zone, both hydrocarbon and water are expected to move. However, dry hydrocarbon production from transition zone is a common phenomenon observed in many parts of the world. Modular Formation Dynamic Tester (MDT) and Drill Stem Test (DST) in three (3) appraisal wells in a high clay volume sandstone reservoir show no evidence of water production in spite of the long perforation interval just above the contact. This could be explained by different reasons depending on the type of reservoir lithology and mineralogy. One of the common reasons in sandstone reservoirs including this case is the presence of Smectite clay mineral in shale, which can immobilize large amount of water.

There are many challenges in characterization and modeling of this high clay volume, dry producing gas reservoir. For instance, how to estimate the amount of mobile and immobile water saturation in the transition zone, how to incorporate the capillary pressure (Pc) data in simulation while still maintaining the production performance, and whether or not the potential reserve and flow characteristics can be captured if petrophysical cut-off applied into the model. This paper will illustrate the case study in characterizing and building the dynamic model with immobile water in transition zone whereas the mentioned challenges are addressed. A novel method is presented to construct the model to estimate the total immobile water saturation using core and log data, and different approaches to initialize the model while evaluating the impact of Pc on reservoir performance are also further discussed.
A Case Study: Validation of Real Time Non-Isothermal Hydraulic Model Using Deepwater Managed Pressure Drilling Data
Authors: Hidayat Andri M. , Irawan Fikri , Karnugroho Ardia
Published: October 2015

Drilling through narrow window between pore and fracture pressure using Managed Pressure Drilling (MPD) approach requires precise hydraulic designs and pressure control plans to achieve drilling to target depth safely in timely manner which require accurate hydraulic model on pressure changes behavior along the borehole.

This paper presents a case study where a non-isothermal hydraulic model was validated using field data from successful Deepwater MPD well in Offshore East Kalimantan, Indonesia. The validation considers all relevant hydraulic parameters such as bottom-hole pressure, equivalent circulating density, circulating friction and surface back pressure. The hydraulic modelling validation results are important in order to determine the non-isothermal hydraulic simulator behavior against actual field data for continuous improvement for future MPD operation.

The validation confirmed the previous theoretical estimations that mud density and annular friction considerably depend on dynamic annular temperature profile. The work revealed that using a field-proof non-isothermal hydraulic model plays critical role in order to gather accurate BHP control in MPD operations.

During the MPD operations, employing real-time hydraulic model validated by PWD data will improve the dynamic pressure control during the operation, the accuracy, and reliability of the hydraulic simulation results. Hence, enhancing the MPD capability to assist drilling a well to zone of interest more safely and efficient.
Application of Bionic Metal Foam with Water Control Technologyfor Sand Control Screen
Authors: Jin Xu , Ding Bin , Chang Liling , Li Jianming , Bi Lina , Liu Yu'e , Long Ying
Published: October 2015

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

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

Gas injection in coalbed methane (CBM) resources is a well-studied method. Findings indicate that although Carbon-Dioxide (CO2) injection expedites the Methane desorption process, its high adsorption affinity causes irretrievable permeability reduction. Nitrogen (N2) injection does not have the swelling issue, however, an early breakthrough of the injected gas occurs. Recently, through several simulation-based and experimental studies, it has been shown that a better result is obtained, when a mixture of CO2 and N2 is injected. In these studies, an optimum composition for the injected gas was found, by carrying out a series of sensitivity analyses for the given CBM with known geomechanical and sorption characteristics. In all of these studies, the composition of the injected mixture remains constant within the period of injection.

In the current work, in order to obtain a better performance, an alternative method is proposed in which the composition of the injected gas is adaptively updated during the injection through several steps. This method can postpone the breakthrough time and also keep well injectivity high. To evaluate the proposed method and find an optimal and practical injection schedule, a semi-synthetic model is constructed. Different injection scenarios are compared with each other, using a compositional simulator (ECLIPSE-300), which uses the extended Langmuir isotherm and the modified Palmer-Mansoori model. The compositional simulation allows us to investigate the sorption competition between each component through the whole system. By a series of sensitivity analyses, an optimum scenario is found. The best obtained scenario, is the one that begins by injecting a mixture with less CO2, and continues by a sequential rise in the CO2 fraction. The outcomes confirm that the proposed method has the following benefits, in comparison with the continuous injection: 1- higher Methane recovery, 2- deferment in permeability reduction, 3- later N2 breakthrough.
How Interpreting Log Data can Improve the Accuracy of Resource Assessment for Shale Plays
Authors: Wong Joanna , Bahar Mohammad
Published: October 2015

The recent developments of shale gas in the US have greatly encouraged exploration for the shale gas resource in Western Australia. The Merlinleigh Sub-basin of the Southern Carnarvon Basin in Western Australia has been found to contain high quality gas-prone source rocks from existing geochemical data. This paper demonstrates how log data can be used in the absence of geochemical data to increase the accuracy of resource assessments. An assessment of the Merlinleigh Sub-basin was used to calibrate and test the reliability and accuracy of the log method.

A major parameter for resource estimation is the thickness of a source rock layer. This is usually determined by geochemical analysis and identifying high TOC intervals from cores. Undeveloped shale gas basins however, are limited in geochemical data whereas most of the drilled wells have wireline log data. Passey's (et al. 1990) ΔlogR method encompasses a multitude of algorithms that predicts TOC from well logs and precisely determines the thickness of a layer. The method is first calibrated with known TOC from cores before applying to wells without geochemical data. Prior studies identified three formation layers in the Merlinleigh Sub-basin; Byro Group, Wooramel Group and Gneudna Formation; potentially containing high quality source rocks. After applying Passey's delta log R method to determine thicknesses, each layer was ranked according to rock characterisation factors such as TOC, generation potential, vitrinite reflectance, porosity and permeability. The Monte Carlo method by Crystal Ball software was then selected to estimate the probabilistic resources of all layers. The production ability of each formation can also be estimated using standard open-hole log data for estimating the Ultimate Recovery in shale gas resources.

In comparison, the TOC calculated from Passey's method produced results consistent with the known geochemical data, thereby validating both sets of data. The Wooramel Group was identified to contain the best quality source rocks, followed by the Byro Group, and lastly, the Gneudna Formation. According to P50 estimations from Crystal Ball, the Byro Group, Wooramel Group and Gneudna Formation contained resources of 51.6tcf, 40.7tcf and 1.4tcf respectively. The Ultimate Recovery for the above was found to be 4.69tcf, 3.71tcf and 0.13tcf respectively. Due to the low estimations for the Gneudna Formation, this paper will focus on the Byro and Wooramel Groups.

This paper explores a unique way of using Passey's method for undeveloped resources having limited log data but no geochemical data. The log data was also used to estimate the Ultimate Recovery based on the production ability of each well. The exploration potential of the Carnarvon Basin in Western Australia for unconventional gas has been identified and is the first geochemical assessment for the Merlinleigh Sub-basin.
Reservoir Sensitivity Evaluation by Monitoring Displacement Experiment with X-ray CT Imaging
Authors: Weifeng Lv , Zhenpeng Leng , Qingjie Liu , Ninghong Jia , Manli Luo , Tong Li , Xu Jin , Jianhua Qin , Zhibin Jiang
Published: October 2015

When designing an oilfield development plan, reservoir sensitivity is a non-negligible consideration due to its direct relation to the formation damage and its influence on the consequence of field output. Traditionally, reservoir sensitivity is evaluated in laboratory by conducting different types of flow experiments from which the variation of core permeability is analyzed. However, due to the lack of sufficient insight vision, this traditional method only reflects the macroscopic phenomena but fails to reveal some important microscopic behaviors inside the core during the process of flooding, such as the fingering of the flooding front, the effective sweeping area or the position of the formation damage, etc. In this paper, a new method, which combined the displacement experiment and the X-ray CT imaging technology, was introduced to effectively observe and characterize the water sensitivity to various flooding scenarios. Formation core samples drilled from the same reservoir layer were used for the displacement experiments while simultaneously being monitored by X-ray CT imaging. The water sensitivity was analyzed by investigating the visualized flooding process from X-ray CT images and quantitatively characterizing the displacement behaviors under differing scenarios. Two new variables, virtual porosity and relative porosity, were proposed in terms of CT numbers in the X-ray CT images to investigate the water sensitivity. It could be shown from the experimental results that the formation damage occurred only near the inlet end where the average porosity decreased by 10% to 15%. Porosity reduction of large pore area was relatively higher than that of small pore area by comparing initial porosity histogram with final virtual porosity histogram. Physical explanation of this water sensitivity phenomenon was deduced that the porosity was reduced by the swelling of chemical reaction product between brine and clay minerals, which resulted in the reduction of CT numbers.
The Impact on Drilling Programme Design of Shallow Gas Detection Using Passive Ultrasound Integrity Survey
Authors: Nussbaum Chris V. , Khlustikov A. , Sarigih J. M. , Reza R. A. , Anuraga E. , Mamesah J. D.
Published: October 2015

This paper is a case study of field data, assessing the impact of a well integrity survey on an on-going development drilling programme, enabling critical management of an unexpected shallow gas risk.

The results and conclusions presented are applicable to the diagnosis and risk management of shallow gas zones and their impact on well construction, design and integrity.

The well Operator experienced a severe loss of well control during drilling operations in the Western Block of Talang Jimar field in Sumatra. The field is mature and the well was considered routine in a series of more than 200 drilled over the past 50 years. A kick occurring at a relatively shallow depth around 300m was completely unanticipated.

It was judged critical to further drilling to investigate the location and extent of the charged interval. This would identify HS&E and operational risks to be mitigated by modification of both the on-going drilling plan and the well design. The clearest and most precise information was required.

When active surface gas venting was discovered at an adjacent well, an ultrasonic annular integrity survey was commissioned to determine the subsurface source of the gas. This ultrasonic survey deploys a number of sensors on wireline in the well, the most important being a passive ultrasound detector.

The paper describes the survey technique in brief, the results of the successful survey and the modifications made to the well and mud-weight design to manage the shallow gas risk and the benefits for the drilling programme.

The new results presented reveal annular flow outside surface casing with clarity, and the paper explores the underlying reasons for this clarity and its potential benefits for shallow-gas applications.

Field data is presented to support the conclusions reached.

The methods and technology described in the paper will be of interest, as they should be widely applicable to shallow gas integrity diagnosis, whether a surface gas vent or sub-surface cross flow, in both onshore and offshore applications. Such diagnosis may enhance drilling and production HS&E performance, reducing the risk of well-control incidents.
The Application of Face Direction Perforating in Unconventional Reservoirs
Authors: Gao Yang , He Liu , Liangang Wang , Yucai Wang , Qinyou Ye
Published: October 2015

The types of reservoirs are more and more complex with the deepening of the exploration and development, and it comes up with a new challenge for perforation completion technology. A new perforating technology is urgent to match up with the reservoirs to improve oil and gas well productivity or create channel conditions for well stimulation, and it is a new requirement to the emergence of unconventional reservoirs. As the middle part of this kind of reservoir development, perforation must be to create a better channel condition for well stimulation, to reduce the rock fracture pressure, induce fracture extension direction, and perfect reservoirs fracture network system. Face direction perforating adopt extra large perforation diameter bullet and special hole arrangement, multi-holes are formed in the same cross section which is perpendicular to the axial of the casing, it can form stress concentration along the wellbore's cross direction, and can effectively control the trend of the fracture, reduce formation fracture pressure, avoid cross collusion of fractures between different segments, and improve the perfect degree of fracture network system. The casing damage research and parameter matching optimizing between casing and face direction perforating are completed by establishing casing damage mathematical model of face direction perforating under different working conditions, the initiation and extend direction of hydraulic fracture after face direction perforating was studied as well, and then it is implemented in the field. Test showed that face direction perforating can reduce formation fracture pressure by 15% or more, oil production increased more than 20% after hydraulic fracture compare with conventional perforating and fracture.
Facile Synthesis of Polyimide Aerogel Usable under Harsh Conditions for the Separation of Oil and Water
Authors: Jin Xu , Xi Tongdi , Liu Xiaodan , Wang Xiaoqi , Sun Liang , Yang Qinghai , Zhang Li , Wu Juntao
Published: October 2015

With increasing environmental awareness, novel strategies to effectively separate oil from industrial wastewaters and polluted oceanic water are highly desired. Using special wettability to design new materials for oil/water separation is an effective and facile way. Herein, polyimide (PI) aerogel is designed and prepared by freeze-drying PI precursor poly(amic acid) ammonium salt (PAS) water solution followed by imidization. With high hydrophobicity, the PI aerogel can be used for the absorption and separation of oil and water. 30–195 times weight of organic pollutants and oils can be absorbed by PI aerogel. To demonstrate the cyclic distillation test, cyclohexane was absorbed by the PI aerogel. As the size and the porosity structures of PI aerogel stayed the same during the separation/distillation cycles, no obvious change in absorption capacity was found after five cycles, indicating the highly stable recycling performance. During separation, water quickly permeated through the PI aerogel and dropped into the beaker below, while oil was retained above it and no external force was employed. Additionally, PI aerogel is also usable under harsh conditions. This research paved the way for fabricating high efficient and recyclable oil/water separation PI aerogel which can be used in the petroleum industry in the future.
Automated Optimization of Interdependent Artificial Lifting Fields Using Integrated Response Surface Model and Hybrid Heuristic-Gradient Algorithm: A Field Case Study
Authors: Ekkawong Peerapong , Kritsadativud Pannayod , Lerlertpakdee Pongsathorn
Published: October 2015

The generic characteristic of producing fields in Gulf of Thailand (GOT) is that oil wells are also developed on the same facilities as gas wells when possible. Different efforts are taken to optimize both oil and gas wells together. Gas-lift is one of the examples of artificial lift that is installed in oil wells. For gas wells, booster compressor (BC) is common facility on platforms to reduce back pressure to each producer routed to the unit. The situation can get even more complex when gas from the BC is used as a source for lifting gas in an oil well.

This paper extends the novel automated optimization workflow of gas field optimization (Ekkawong P. et.al. SPE-173450) and oil field with gas-lift optimization (Kritsadativud P. et.al.SPE-174039) to maximize production from more complicated gas/oil fields with various combined artificial lifting systems. Firstly, to improve calculation efficiency, the production performance estimated by NODAL analysis is transformed into a multi-dimensional response surface model (RSM) as a relationship between flowing pressure, gas injection rate and oil production. This transformation significantly eases the computation burden. The RSM is then used as the well performance prediction tool to be used in a production optimization workflow using hybrid optimization algorithm, the combination of heuristic and gradient based optimization. Genetic Algorithm is roughly searching for the global optimum solution, and then the gradient based method is used to further refine the solution. The process is run repeatedly with different initial guesses to ensure the optimality of the obtained solution.

The benefit of this method is demonstrated in a synthetic field that illustrates the complex offshore field in GOT. This field features oil and gas wells with interdependent artificial lift equipment: gas-lift and BC. The objective is to maximize field oil/condensate production under other field operating constraints. The controllable parameters are: amount of gas to be injected into each oil well, well to be routed to BC, and wellhead flowing pressure from each well. The result of this proposed workflow shows increase in oil production honoring all practical constraints. Additionally, the computation time is also significantly reduced from the conventional approach using manual fine-tuning and the integrated NODAL analysis modeling.

This automated workflow simplifies the more complex process to be a much more computationally efficient and easy to understand. Hence, it can be used as the tool to optimize day-to-day production operations in the complex fields that the conventional tool is obstructed by the computational burden.
Preformed Particle Gel Propagation Through Super-K Permeability Sand and Its Resistance to Water Flow During Conformance Control
Authors: Imqam Abdulmohsin , Bai Baojun , Delshad Mojdeh
Published: October 2015

Excess water production has long been considered a major problem leading to the life-shortening of oil and gas wells and operational problems. High-permeability streaks, fractures, conduits, and fracture-like features can expedite an undesirable water channeling and early water breakthrough during water flooding. Preformed particle gel (PPG) is one of the commercial gels invented exclusively to plug such features to reduce excess water production, improve sweep efficiency, and increase oil production. This paper reports the results of laboratory experiments that studied the PPG's injection and placement mechanism through Super-K permeability cores to reduce unwanted water production and increase oil recovery. Extensive experiments were conducted to examine the effect of the sand permeability, PPG size, concentration, and water salinity on the PPG injection process, passing criteria, and plugging efficiency to water flow. A two foot sand pack model with four pressure taps was designed to monitor PPG transport and plugging performance. The results showed that the PPG propagated deep into the sand pack. PPG's in-depth permeability reduction to the core was dependent on the PPG size, strength, concentration, and sand permeability. Fully swollen gel particles had better injectivity than partially swollen particles with a larger diameter size; particle strength was more dominant in influencing particle movement than was particle size. The injection pressure increased as the PPG concentration, water salinity, and gel particle size increased. A large injection pore volume was required for the PPGs to be produced at effluent when both the water salinity and particle size were increased and when the PPGs concentration decreased. PPG transport through Super-K permeability sand exhibited three patterns of injection processes based on both the threshold pressure and the injection pressure measurements across the sand pack cores: low gel particle retention and pass; high gel particle retention and pass; and high gel particle retention, breaking, and pass. After the PPG injection process was completed, cycles of saline water were injected into the sand pack to test the PPG's resistance to water flow. The PPG's blocking efficiency to water flow increased as the PPG strength, size, and concentration increased. The PPG placement mechanism, such as washout, was also found to considerably affect the water injection flow processes. The results of this laboratory experiment will aid in the selection of future conformance control candidates and also optimize the particle gel treatment design for large-scale field projects.
Novel EOR Strategy-Decision System Based on Delphi-AHP-TOPSIS Methodology
Authors: Liang Bin , Jiang Hanqiao , Li Junjian , Gong Changcheng , Ding Shuaiwei , Mi Lidong
Published: October 2015

EOR strategy decision has been considered as a thorny process, which depend on proper evaluation, rational understanding of the complex relationships, and quantitative assessment of the multiple relevant factors, including economy considerations, dynamic field production, reservoir numerical simulation and other related factors. A decision making system based on Delphi-AHP-TOPSIS methodology is developed to meet this challenging problem, and the technological process is divided into three phases. The first phase is Delphi method, where analysis of undisturbed, identification according to professional theories and quantitative evaluation of key performance factors and sub-factors are implemented and an effective measurement scale is carried out. The second phase is Analytic Hierarchy Process (AHP) based on EOR performance of several selected strategies, so as to investigate EOR performance of correlative factors and sub-factors, along with synthesis influence of the factors. What's more, the third phase is Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) depending on evaluation of candidate solutions whose utility function show monotone decreasing or increasing characteristics. A typical EOR strategy case is presented for better understanding, which is known as polymer flooding strategy. The proposed strategy-decision methodology has proved useful for decision making, helping engineer acquire more comprehensive understanding of the relevant factors in existing scheme and choose the better alternatives. The approach can not only minimize decision makers' bias, combining influence of financial and technical factors, but also facilitate the decision makers to make the best response to the oil market and the reservoir dynamic performance rationally. The proposed system is successful application of the Delphi-AHP-TOPSIS methodology for EOR scheme decision, through the Delphi, the quantitative evaluation of the influencing factors can be obtained without inappropriate analysis and the AHP and TOPSIS procedures can identify better practices from the analysis of the comprehensive influence of individual factors and sub-factors. Thus the optimal EOR strategy can rise to the surface.
Decision Support System on Pipeline Replacement of 200 kilometers Main Oil Transport Pipeline in a Very Mature Oil Block
Authors: Azwar Noezran , Migas SKK , Agus Pramudyana
Published: October 2015

Objectives/Scope

The objectives of the research are to establish decision support system for pipeline replacement. The scope of the research is 2005 – 2014 inspection data on 200 kilometers main oil transport pipeline in one of mature oil block under Production Sharing Contract. The incident varies from small leak, rupture, congeal, and to the most: hit by trucks incidents.

Methods, Procedures, Process

Research starts in 2005 – 2014 after first leak in 2005. The research performed with many investigation methods, from visual inspection, in line inspection, long-range ultra-sonic method, to magnetic tomographic method. Results from those investigation used for short-term action and used for risk analysis. Risk analysis conducted from process hazard identification and analysis, to risk based inspection analysis. SWOT analysis also performed to make conceptual decision for the replacement. Front End Engineering Design (FEED) was conducted to replace the pipeline. Quantitative Risk Analysis for new pipeline is included in FEED.

Results, Observations, Conclusions

Pipeline inspection performed since 2005 shows there were significant wall thickness loss at the pipeline. Short-term action has performed by installing pipe metal sleeve. This procedure significantly reduces numbers of leak incident. The predictive and preventive maintenance is performed every year to assure safe pipeline operation. Inspection on right of way shows significant population growth along the pipeline route. Inspection shows rapid growth in land encroachment, illegal crossing, and illegal tapping activities along right of way. Police records shows "pipeline hit by truck" occurred every year. Short-term action has already performed to protect the right of way including access limitation, hazard signs, and fencing. Unfortunately, these actions do not reduce the numbers of incident significantly. All inspection data and records become inputs for process hazards analysis and risk based analysis. Risk based analysis shows most of 200 kilometers pipeline sections are exposed to high risk. Pipe metal sleeve do not reduce overall risk significantly yet. Pipeline is highly exposed to third party risk. SWOT analyses shows pipeline replacement with new route are required to significantly reduce the calculated risk.

Novel/Additive Information

This paper shows a structured decision support system is required in the very first step of project to make conceptual decision massive pipeline replacement in a very mature oil block.
Reservoir Characteristics for Unconventional Shale Play of Huai Hin Lat Formation in Northeastern Thailand
Authors: Chumkratoke C. , Dunn-Norman S.
Published: October 2015

Recent trends in petroleum production have focused on developing unconventional gas reservoirs such as tight gas and shale gas. Considering worldwide shale gas resource potential, the largest reserves exist in the former USSR and in North America, while for China, Central and Southeast Asia the estimated shale gas reserve is 1115 TCF. Despite the smaller reserve projection, this unconventional resource is of great interest for future development. In Thailand, the primary energy source is oil and natural gas, with 77% of electricity generated from natural gas (EIA, 2011). Yet current production is not enough to support the growing energy demand in Thailand, and there is increasing emphasis in exploring potential unconventional resources to meet this demand.

A study has been conducted to improve reservoir knowledge of the Huai Hin Lat formation, believed to be an important source rock for the gas fields in northeast Thailand. The Huai Hin Lat formation consists of fluvio-lacustrine sediments of Late Triassic. The formation is exposed along the margin of the Khorat Plateau. Petroleum exploration in Khorat Plateau has been ongoing since 1962 and two gas fields have been discovered and commercially produced in the Khorat Plateau since 1988.

Seven shale samples were taken from the Huai Hin Lat formation. All samples are the organic rich fine-grained rocks. The MicroCT technique was measured for porosity paramter. The average porosity of the samples was approximately 4.9%, and a pore size distribution was found. In addition, geochemical analysis was performed to determine total organic content (TOC) of the shale samples. The average TOC was found to be approximately 4.9%.

Permeability was measured for the seven samples using transient pressure pulse decay. The permeability range of the samples was found to be 90 nD to 280 nD and the average permeability of sample was approximately 180 nD. Permeability varies significantly because of the shale is somewhat heterogeneous.

This paper provides details regarding the analysis of the Huai Hin Lat samples and the shale's rock properties as they relate to other commercial unconventional gas resources. The work is significant because there are few existing petrophysical evaluations of this formation. Results from this study will identify and highlight key reservoir parameters necessary to further assess the commercial potential of the Huai Hin Lat shale as a shale gas reservoir.
Jointly-Developed Novel Torque Transducer Ensures Jack-up Rig Integrity
Authors: Wang J. K. , Delves C. , Li D. W. , Cooper M. , WU J. W. , Van Millingen J. , Qiu T. S. , Sleath C. , Wang J. M.
Published: October 2015

To ensure the integrity of offshore jack-up rigs, a novel torque transducer has been developed through 18-month-long joint collaborations cross industries globally.

A medium size offshore jack-up rig uses a set of fifty-four units of AC-driven jacking systems to jack the platform up and down. Due to inevitable manufacturing tolerances and poor correlation between motor current and its torque at standstill and near-zero speed, the synchronization and even load distribution among the fifty-four climbing pinions of these jacking systems has been a challenge. Uneven load sharing among these fifty-four climbing pinions can overload and then break some of them prematurely. Broken climbing pinions can result in catastrophic rig accident and human casualties.

This novel torque transducer measures the climbing pinion resistant torque directly through reading the torsional deflection of the pinion precisely. A series of design verification through finite element analysis and design validations through factory acceptance tests have been conducted successfully.

With this new torque transducer installed, the load on each climbing pinion can be read simultaneously and then controlled either manually or with a variable frequency drive.

Different from any existing standard torque transducer mounted between electric motor and the input shaft of jacking system, this new novel torque transducer is designed to be mounted inside the climbing pinion and then reads the torque load on the pinion directly. The accuracy of this direct torque reading is regardless of the gear transmission efficiency, which, in fact, governs the reading accuracy of the current existing standard torque transducers available in the market.
Laboratory Investigation into Wettability Alteration by different Low Salinity Water Compositions in Sandstone Rock
Authors: Shabib-Asl A. , Ayoub M. A. , Elraies K. A.
Published: October 2015

Low salinity water flooding is not an infant practice in petroleum industry; in fact, it has prevailed for several decades. Due to its significant contribution to the hydrocarbon recovery, the method has widely gained the attention of many researchers. From its early breakthrough, many studies have been conducted which have focused on comparative analysis between the low and high salinity water. Moreover, it has been verified that most of them were effective at brine concentration below 5000 ppm. With the purpose of enhancing oil recovery, low salinity water (LSW) with adequate composition and salinity is injected into the reservoir, which changes the wetting properties of the reservoir rock into those favoring oil recovery. However, the true mechanisms behind the process are still questionable and there is no specific optimum salinity range and type to be recommended.

The present study investigates the wettability alteration on Berea sandstone rock with brine of different ion compositions and salinities. Measurements were performed on a set of 31 sandstone core slices primarily saturated with formation water and then aged in crude oil at 80° C and ambient pressure. All slices were removed from oil and aged with different low salinity water and formation brine at same conditions. The low salinity water consisted of 30 samples of different compositions with concentrations ranging from 500 to 6500 ppm. The formation water contained high concentration of magnesium and calcium divalent ions (i.e., Mg+2 and Ca+2) at 130,000ppm. The examination of wettability alteration was performed by using the sessile drop method at specified ranges of time. The results revealed that significant change in wettability was observed with the low salinity water composition of potassium and sodium monovalent ions (i.e., K+ and Na+) as compared to the divalent cations of Mg+2 and Ca+2.
CGDS Near-Bit Geosteering Drilling System and Its Application in China
Authors: Gao Wenkai , Sheng Limin , Dou Xiurong , Zhang Lei , Su Yinao , Wang Jiajin , Deng Le , Li Lin
Published: October 2015

Directional wells and cluster wells have become a conventional drilling technique now, which is widely used in various types of oil and gas reservoirs. Each year, more than half of the total drilling are directional wells in China. The main work is not to aim the target area, but to track the reservoirs now. Geosteering drilling is an important technical approach to improve single-well production and recovery ratio, to achieve the "less wells more production" idea.

China Geosteering Drilling System (CGDS), integrated the technology of drilling with logging and reservoir engineering, applies the near-bit geological and engineering parameters as well as controlling method to ensure that the wellhole trajectory can pass through reservoir and get best location while drilling. The wellhole trajectory can be adjusted and controlled timely according to the formation features measured by CGDS. The drilling bit is equipped with "eyes", which can identify oil/gas layer during drilling.

The CGDS is configured with CAIMS(Adjustable Instrumented Motor System), WLRS(Wireless Receiver System), GGMWD(Geosteering MWD System), CFDS(China Formation/Drilling Software System). More than 140 wells in China have demonstrated the system's ability to increase the probability of penetration and recovery rate in complicated formation, to reduce drilling costs and increase production and economic profit.

On the basis of introduction to the system, this paper focuses on the recent achievements as well as the lessons learned from the application in China. Helpful case histories will also be presented.