bluuebunny/crossref_metadata_2025 huggingface dataset:
Hawiyah Gas Plant Alarm Rationlization and Controller Performance Monitoring
Authors: Almubarak Yousef H.
Published: May 2016

In order to improve the plant and operation efficiency and reliability, HGP established a consistent and standard methodology for the development, implementation, and modification of process and system alarms. In addition, this methodology serves as guideline to monitor, fix and report bad actors in alarms and PID controllers. The task involves a comprehensive study to the entire plant alarms database including settings, grouping, priorities, philosophy and configuration. In addition, this task will ensure the continuity of PID controllers monitoring to ensure that all of the plant PID controllers are in auto and they are maintaining their set point. Succeeding to achieve this will ensure the optimum performance and efficiency and ensure more vigilant operation. HGP succeeded to bring the controller in auto to above 90%and a full alarms rationalization study was conducted to bring the alarms level to the international KPIs.

The paper will start with providing basic background about essential definition including the alarms, alarm rationalization and controller performance monitoring. Then, the paper will address the importance of the subject and the need of the improvement. As there are many recent studies indicates that missing critical alarms lead to fatal insidents and major damages to different facilities. In addition, many of the plants upset and changes could have been avoided if good alarming system is in place. Beside all of this, the paper will address the importance of the plant controllers'automation as having these valves on auto will assure having the targeted product with the best possible efficiency.

Then, the paper will address the basic effort and plans Hawiyah Gas Plant conducted.

In the first section of the effort, the paper will address the alarm rationalization and monitoring effort with the goal to bring the plants alarms to the acceptable limit where only the required alarms will be received by the operator. In addition, all of the alarming system is based on best of practice configuration with the right color code, disception and presentation. To assure that the received alarms are meanenigful and they require operator action.

This section is divided in two parts: the alarms rationalization effort and the alarm monitoring part.

For the first part, the paper will address the newly plant developed alarm philosophy that act as the base of the Distrbuted Control System (DCS) alarms configuration. And the tools used to generate the alarms reports and how this set up is ideal for such service. In addition, the paper is highlighting the team and task force that it takes to accomplish the task as such critical task has to be attended by a multi disciplinary team. Then, this part will discuss the developed and utilized KPIs which they are related to the number of alarms received at each console, the peak alarm rate, the inhibited alarms, chattering and stale alarms.
Boilers Reliability Study- Abqaiq Plants Experience
Authors: Al-Alamoudi Saeed A. , Al-Hajji Mohammad H. , Al-Suwaian Mohammad S
Published: May 2016

This paper describes a reliability enhancement study for boilers that was recently conducted at the world's largest crude oil stabilization plant in Abqaiq, Saudi Arabia. Since its inception in the 1940s, the Abqaiq plant has had to operate a number of water tube boilers to produce high pressure steam that is used to process stabilized oil. In each boiler, there are more than 2,000 tubes and, over the years, several boiler tube failures have occurred. This paper describes a recent study that was conducted to evaluate the history of tubes failure, identify the main factors of the tube failures, and generate recommendations to minimize the number of failures. This paper presents the results of a recent boiler life assessment study that was conducted on one of the boilers at the Abqaiq plant.
Performance of Refracturing in Multiple Thin Layers of Low Permeability Oilfields
Authors: He Liu , Wenjun Wang
Published: May 2016

For the low permeability formation of Daqing oilfield, we have to stimulate the multiple thin layers in one stage during a separated layer fracturing job because there are many of layers in one well. Based on the logging data analysis, the hard fracturing layers identified method has been built for the multiple thin layers re-fracturing in low permeability layers in Daqing. According to the calculating result of the broken pressure difference within multiple layers, we can recognize the layer which is not been stimulated in the first time multiple layers limited entry fracturing job. We can optimize the fracturing parameters design in the re-fracturing treatment. Based on the research of interference disciplinarian between fractures, we can get the boundary of the least interval without the interference. So we can analysis which layer is not been stimulated enough because of fractures interference in the first time fracturing. Researching the relationship of perforation holes erosion with fracturing treatment parameters can help us to estimate the first time fracturing and optimize the re-fracturing treatment parameters designing. By using above method, we have got a satisfactory re-fracturing result in 27wells. After fracturing, the oil production is increased 6.8t/d and the water ratio is decreased 4.2%. The oil production is even higher 1.2t/d than the first time fracturing. That shows the new layers have been stimulated.
Employing First Principles Model-Based Soft Sensors for Superior Process Control and Optimisation
Authors: Lee Shuyee D. , Zahrani Aidhah J.
Published: May 2016

This paper describes the development and implementation of soft sensors at the world's largest crude oil stabilization plant (Abqaiq) for superior process control and optimization. The soft sensor uses a rigorous steady-state model combined with dynamic synchronization to compute real-time stream properties (i.e., hydrogen sulfide amount (H2S), Reid vapor pressure(RVP), and true vapor pressure (TVP)) so corrective action can be taken immediately. Crude oil is characterized by 19 pure light components and17 heavy pseudo-components. A non-Random Two-Liquid (NRTL) model is used for predicting thermodynamic properties of the liquid phase while an ideal gas model is used for the vapor phase. Unlike traditional data driven methods, the soft sensor adopts the first-principles modeling approach so current operating conditions can be correctly reflected in the online model based on sound engineering principles. Fault detection, sensor validation, and calibration with laboratory data are also performed online to ensure reliable and accurate predicted H2S, RVP and TVP values.
Assessment of Corrosion and Mechanical Properties Degradation of Pipeline Steel After Long Term Service in High Sour Gas-Field Environments
Authors: Zhang Cheng , Zhang Qingsheng , Chen Weiguo , Liu Dexu , Ou Tiongxiong , Huang Xuesong , Chen Can , Chen Changfeng
Published: May 2016

In this work, the corrosion behavior and mechanical degradation of two types of pipe steel, Inconoy 825 and L360, after two years of high sour environments service in Puguang gas-field were studied. Results demonstrated that a fearful elemental sulfur layer deposited on the inner wall of pipeline, pitting corrosion and hydrogen-induced cracking was observed in L360 pipe. In comparison, no pitting corrosion and hydrogen-induced cracking was found in Inconoy 825 steel pipe due to its excellent resistance to corrosion. Furthermore, mechanical properties (yield strength, impact strength, elongation, hardness, fracture toughness) and stress corrosion cracking were investigated. Results showed that the yield strength decreased obviously and the percentage of elongation increased in Inconoy 825 steel but little change in L360. The analysis a change of the mentioned mechanical characteristics together with the results of the diffusion and tapping of hydrogen of them indicated that the properties degradation of Inconoy 825 pipeline steel after long term service was associated with essential role of hydrogen in these processes.

The consequences of sudden failures and severe corrosion of metallic material in the high sour gas-field, which associated with their exposure to H2S/CO2 containing gas, led to the preparation of evaluation tests of pipeline. However, passing evaluation tests cannot guarantee the safety in actual work condition unless the field experience had been at least two years. As the first attempt to exploit high sour gas-field in China, it is anticipated that this work of Puguang provides valuable data and an essential insight into the corrosion and degradation of pipeline steel services in high-sour environmental.
Achieving Brazilian Extended Reach Drilling Records on Polvo Project with Ultra High Torque Connection
Authors: Biddle Nathan , Osorio Luciana , Arevalo Hector , Velho Marcelo , Flores Vincent , Granger Scott
Published: May 2016

The Polvo project is a platform based drilling rig located ~95km off the Brazilian coast in the Campos Basin. The field consists of two distinct reservoirs, a carbonate reservoir to the southwest, and a sandstone reservoir to the east. The Polvo project began drilling in March 2007 and has since drilled a total of 32 wellbores. The wells range in difficulty from "shortreach" to "very extended reach" wellbores. The deviation is from 3–7º DLS at angles of 30–92º. Wellbores are 3-dimensionally designed in order to improve total reservoir exposure.

Extended reach, deep and high deviation wells require the use of a drill string that has both higher torsional yield strength drill pipe body and greater torque capacity tool joints than are afforded by standard API connections. VAM Express double shoulder connection has been designed in order to address the drilling challenges linked to the development of such complex wells. This proprietary high torque connection incorporates four major design features allowing pushing further the drilling envelope limits: quick rig make-up, high torque performance, user friendly and durability.

After beginning the project and platform placement, it was discovered that sandstone reservoir targets further to the east had higher productivity than expected. After drilling 12 wells and numerous lessons learned, the furthest extended reach well in the history of Brazil was attempted and successfully completed.

The Pol-O wellbore was drilled to a total measured depth of 6,489 m (2,429 mTVD) and a vertical section step out of 5,615 m. This wellbore was and continues to hold the record for furthest reach wellbore in the history of Brazil.

In addition to obtaining this extended reach record, Polvo also attained the record of fastest 24 hours drilling in an 8 ½" hole with 1,610 m in 24 hours. To obtain this drilling record, it was not only critical to have high on bottom ROP, but also to optimize connection time. The high torque connection helped to achieve this fast connection time and also prevented any drill string failure.

Having drilled over 100,000m of total hole in highly deviated wellbores using the same drill string, there has not been any twist-offs or back-offs on the Polvo project.

By being able to drill these further reach wellbores successfully and more economically, the Polvo Platform has proved up further reserves that can be produced without requiring installation of another platform or subsea tiebacks. The rig is not limited by connection strength and plans are in place to improve the top-drive to deliver more torque, while staying with the same double shoulder connection size.
A Case Study : Innovative Open Hole Well Completion Provides Superior Results in Tigh Gas Formation in Jilin District, China
Authors: Feng Wang , Liu Changyu , Zhang Yingan , Wang Yong , Liu Hai , Tong Ku Ka
Published: May 2016

Drilling of horizontal wells has increased steadily over the last few years in China on land. As technology has developed, operators have seen the economic and production benefits of drilling horizontally 1, 2. In the Changling gas field, the Deng Louku formations are primarily low porosity (average 5.2%) and low permeability (average 0.17md) tight sand. Typically, wells in this area are drilled vertically and completed with cemented casing. Proppant fracturing was necessary to produce the well economically due to the low permeability nature of the formation. However the production results from the conventional vertical fracturing completions were not very promising and most of the wells experienced rapid production decline once they were put on production. Thus it became crucial to find an engineering solution to effectively unlock the reserves and obtain sustained long term productivity.

Multistage fracturing of the DP2 horionatal well is a milestone for the operator due to:the deepest, and most stages in a single horizontal well in a tight sand formation in China was completed and fractured;the biggest fracturing job for a single well in terms of proppant and fracture fluid volume was successfully pumped continuously by first time application of the precise continuous mixer (PCM) in China;an innovative multistage fracturing design workflow was developed to optimize the horizontal well completion design including several disciplines: geology, reservoir modeling and fracturing.

This workflow was set as the standard design process for multistage fracturing design in the field.

The DP2 horizontal well was completed in ten stages in the 837 m openhole section and the ten fracturing stages were pumped continuously in 3 days. The PCM was used to improve the fracturing operation efficiency. A total of 1425 tons of 30/50 proppant was successfully placed into the formation using 4870 m3 fracturing fluid. The well produced 320,000 m3/day initially and was stabilized at 180,000 m3/day with 20 MPa wellhead pressure, which is 5 times higher than the average offset well.

The application of real time hydraulic fracturing monitor technology helpped to verify that the optimized fracture half-length was achieved, and to adjust the fracturing schedule in real time for the second stage.
New Hybrid Bit Exceeds Expectations in Challenging Application in Tarim Field, China
Authors: Nicholl Denise , Garcia Alexis , Barocio Hector , Sha Dennis , Jian Zhou
Published: May 2016

The existence of hard, interbedded formations often prove to be very damaging to conventional polycrystalline diamond compact (PDC) fixed cutter bit designs, and as a result, may require additional trips to replace the bit for insert roller cone or impregnated diamond. This can represent significant additional drilling costs for the operator, equating to very high costs per foot if the remaining section to be drilled is short. The challenge is to maintain a low cost per foot, through the use of a bit design which is both durable enough to drill the desired interval, at the best possible penetration rate.

This paper describes the development of a new innovative drill bit technology that fuses two existing fixed cutter materials using a unique design philosophy that allows for greater versatility in drilling a wider range of interbedded, difficult to drill lithologies that are not typically drilled entirely with PDC bits. This novel design philosophy includes optimized cutter placement allowing engineered exposure of diamond impregnated mix applied in critical areas of the bit for added durability.

This development project was initially targeted for the sub-Saharan region in the Congo, where the existence of a conglomeratic interval at the bottom of the section prevented to reach total depth (TD) with fixed cutter bits, having to end with roller cone insert designs. In its first trial, the new design drilled three times the interval of the best offset with a 34% improvement in rate of penetration (ROP).

Applications in different regions of China were soon identified, resulting in a challenge to design for a new hole size with various drive types; the results of which are detailed in this paper.
A Comprehensive Formation Evaluation Method to Make the Fracturing Decision: A Real Case Analysis from a Low Permeability Formation in Jungger Basin of China
Authors: Wang Ben-Cheng , Nie Ren-Shi , Xu Jiang-Wen , Wei Shao-Bo , Hu Guang-Wen , Zhang Jun-Ming , Feng Meng
Published: May 2016

Low permeability formation is the main exploration objective in China. Too much misjudgments of fracturing operation would tremendously increase the cost of exploration. We studied a method to estimate the well productivity for a Permian low permeability formation in Junggar Basin of China. Firstly, we made a statistical analysis to the lithology according to logging data and divided the lithology into 7 categories. We developed a set of standards to mark the seven categories. Secondly, we made a statistical analysis to 6 parameters of physical properties, such as porosity, permeability. We also developed a set of standards to mark the physical properties. Thirdly, we made a statistical analysis to DST data and divided the log-log curves of DST into 5 categories. We defined a pressure recovery rate that can reflect the formation energy status and analyzed the characteristics of the pressure recovery rate for different category DST curves. We marked the 5 categories DST curves and its pressure recovery rate. Fourthly, we made a mathematical statistics to the relationships of fracturing productivity with static and dynamic parameters, including pressure recovery rate, sand volume and fluid volume of fracturing. We obtained the productivity prediction equations by using multiple nonlinear regressions to static and dynamic parameters. Fifthly, we needed to use the method of the above 4 steps to mark the lithology, physical properties and DST of a new well and estimate productivity. Finally, we made a suggestion of fracturing to the new well. We applied the comprehensive formation evaluation method to 12 new wells of the Permian low permeability formation. Compared with the real oil-testing results after fracturing, the judgment accordance rate is 75%. The researched method can be generalized to other low permeability formation.
3D Seismic Attributes as Exploration Tools: A Case Study from the Late Jurassic Hanifa Formation in Saudi Arabia
Authors: Liu Libin , Kharji Mohammed , Chatterjee Himadri S.
Published: May 2016

The Arabian Gulf, in Saudi Arabia, is a mature petroleum province. As exploration moves from structural concepts to the stratigraphic domain, identifying petroleum system elements in areas with limited well control becomes imperative to cost-effective exploration. Explored areas are blessed with reliable datasets (most significantly well data) that records subsurfacerock properties. In exploratory areas with very sparse well control, seismic is the most appropriate data set currently available for approximating rock properties. Therefore, finding reliable seismic attributes that correlate to rock property variations in well logs holds the key to exploratory success.

This paper presents the results of a project undertaken to identify seismic attributes that differentiate between source and reservoir facies within the carbonate Hanifa Formation in the Eastern Province of Saudi Arabia. A detailed analysis of wireline logs from wells suggests that rock properties like velocity, impedance, Lambda Rho and Mu Rho are higher in carbonate source facies under consideration than their reservoir counterparts. Impedance computed from seismic inversion is found to be in consonance with that derived from wireline log data. Projected facies are found to fit predictions of the geological model in wells in the study area. Mapping of impedance in the 3Dseismic volume helps carry the interpretations from the known to the unknown. Acoustic impedance, derived from seismic inversion, thereby offers promise as a tool for identification of petroleum system elements in areas with very sparse wells.
Cementing Through Capillary Tubing to Meet Regulatory Requirements: A Novel Approach for Plug and Abandonment
Authors: Wilde Jason , Ellis Todd
Published: May 2016

Capillary tubing has traditionally been used for various downhole chemical treatments applied to enhancing fluid loading, treating corrosion and scale buildup, and preventing paraffin and emulsion formation. Capillary tubing provides an advantage over coiled tubing due to its lighter weight, smaller footprint, mobile structure, faster running speeds, and more economical costs. One drawback however, is the increased friction pressures when pumping abrasive fluids. Typical capillary tubing is sized from ¼ to ¾ in. OD versus the more common coiled tubing, which ranges from 1 to 3 ½ in. OD. Therefore, the use of capillary tubing for cementing operations has not been considered until recently.

This paper will feature a project in Australia where a capillary unit was employed to abandon a well with cement, while concurrently installing downhole pressure gauges to comply with local regulations. The cement design criteria along with two case histories will be described, and lessons learned will be evaluated.

Data that has been collected through the various jobs will demonstrate that current simulation software will need to be modified to match pressure outputs witnessed in the field. A comparison of simulated versus actual job pressure data has shown as much as a 70% friction reduction in actual pressure readings. The witnessed pressure values are shown to be consistent over several operations; therefore a theoretical correlation can be drawn so more realistic values can be simulated in the future. Additionally, slurry designs which were proven successful and operational considerations for improved job quality will be discussed.

This paper will discuss two case histories in which capillary tubing was used for the first time in Australia. Methodology, limitations, and future improvement possibilities will be discussed in detail throughout this paper.
Multi-Tubular Corrosion Inspection Using a Pulsed Eddy Current Logging Tool
Authors: Rourke Marvin , Li Yong , Roberts Glyn
Published: May 2016

Tubular inspection can be split between direct measurements such as caliper logs or downhole video observation and Electromagnetic (EM) methods that measure properties sensitive to pipe thickness, with wall thinning associated with corrosion and other pipe defects. Various EM methods have been reported over the years often initially for pipeline inspection and then adapted for downhole well monitoring. These methods include Magnetic Flux Leakage (MFL) and Eddy Current (EC) measurements. Early EM methods were single frequency but later developments include multi-frequency. In this paper we report an emerging technique called Pulsed Eddy Current (PEC) which is inherently multi-frequency and in time domain is radially sensitive which enables inspection of multiple tubular thicknesses. Most inspection techniques including some EM methods are only capable of inspecting the inner most tubular or only the total thickness of multiple tubulars. However, a PEC tool can measure separate thicknesses of both inner and a second tubular. This allows quantitative corrosion evaluation of casing without removing the completion tubing.

The paper covers a theoretical review of the PEC technique and development of a fast forward analytical model tied to experimental data acquired with an actual logging instrument. The fast forward model is used to ensure optimum tool design and allows development of an inverse model which realises quantitative evaluation of the corrosion within multiple tubulars from field data.
Development Optimisation of a Marginal Oil Field in Bohai Bay China - Integrated Solutions to Overcome Challenges in Offshore Horizontal Well Construction
Authors: Nie Chaomin , Zhao Yongsheng , Tan Lv , Jia Yong , Zhai Gang , Halomoan Parlindungan Monris , Hui Xu Chong , Yong Wang , Fei Wang , Jianyi Dong
Published: May 2016

A total of nine horizontal wells including one injector well were drilled to cover the small, 9 km2, oil-bearing area of a marginal oil field that is isolated by secondary faults and stratigraphic depositional borders in Bohai Bay, China.

A pilot study showed that the reservoirs are distributary channel sands of a shallow water deltaic depositional system. Seismic inversion indicated that the sand properties and connectivity vary dramatically across the field. A multiple-aquifer system was apparent, and the gas/oil contact (GOC) and oil/water contact (OWC) levels were unknown. Furthermore, the only well control was from three vertical exploration wells and two directional offset wells.

An advance distance-to-boundary well placement technique using azimuthal deep directional electromagnetic logging-while-drilling (LWD) technology was applied to overcome these challenges and to enhance reservoir understanding. A multifunction LWD formation evaluation tool was deployed to evaluate fluid properties where the top gas might occur. In addition, a rotary steerable drilling system (RSS) was assembled to achieve drilling efficiency and smooth trajectory control.

One injector well and eight producer horizontal wells were precisely placed in optimum position for injection and drainage with a 100% success rate; one producer horizontal well was retracted while another producer well was added based on finding definite GOC and OWC levels. Increasing the drilling penetration rate and avoiding adjustments following reservoir exits led to a 60% improvement in drilling efficiency, which is equivalent to a cost savings of USD 32 million. Production from these horizontal wells surpasses the set production target by 30%, with extremely low water cut. The integrated LWD, well placement, and RSS solution optimized the marginal oil field into a much more economic development oil field.
Successful Development of Thin Zones: Challenges and Strategies
Authors: Al-Julaih Ali , Taibah Obai
Published: May 2016

Thin reservoirs that are only a few feet in thickness present a clear challenge to development specially when coupled with fractures, lateral heterogeneities, and structural uncertainties. This paper discusses the challenges associated with the development of a thin zone located at the top of a carbonate reservoir as well as the strategies implemented to overcome these challenges and develop the zone successfully.

Due to the lower rock quality when compared to the underlying zones and extreme thinning, this zone could not be produced through the conventional vertical wells historically. Through the strategic monitoring program implemented in the field, an opportunity to place direct production from this zone has been identified specially in the mature areas of the field where the lower zones are fully swept after decades of continuous production whereas a thin zone at the top of the reservoir is unswept. Capitalizing on this opportunity, a strategic development plan has been initiated. This plan calls for placing horizontal laterals in this zone utilizing recently developed fit-for-purpose well placement and completion technologies.

To successfully develop this challenging zone, several strategies have been implemented. First of these was strategic well planning where a systematic methodology was implemented to evaluate and develop this zone. The most promising target areas were located through comprehensive evaluation of the area, with detailed geological modeling. Secondly, advanced geosteering with a rotary steerable system (RSS) has been utilized to efficiently place laterals in the upper lobe of the targeted zone. Advanced completions, using inflow control devices (ICDs), were utilized as a fit-for-purpose to mitigate the counter effect of fractures and/or pressure differences across the horizontal section. The development program has been very successful in yielding significant production gains.
Sour Gas Amine Filtration Enhancement
Authors: Khan Asif
Published: May 2016

Saudi Aramco Gas Operations can process over 8 BSCFD of gas. Diglycolamine (DGA) is the most widely used Amine in gas treatment facilities. Similar to other types of amines such as monoethanolamine (MEA), diethanolamine (DEA) and methyl diethanolamine (MDEA), the performance of DGA is mainly reduced by accumulation of contaminants, e.g. suspended solids, hydrocarbon liquids and degradation products. Foaming, solvent loss, fouling and other operational problems are associated with DGA contaminants in high-pressure (HP) DGA systems. Low pressure systems generally have more stable performance with less operational issues. These issues are generally managed by anti-foam injection, fresh solvent addition and installation of mechanical filters.

The gas treatment system is equipped with inlet gas filtration and amine filtration to reduce the contamination level in DGA, e.g., suspended solids, pipe corrosion due to aging and hydrocarbons. Slug catchers remove the bulk of liquid in the gas. Three phase separators with coalescing element remove liquid aerosols and solid particulates. DGA filtration consists of a pre-coat filter (1 micron rating) and a mechanical filter (5 micron rating) installed on a slip stream.

The pre-coat filter consists of diatomaceous earth (diatomite or kieselguhr) coating material bonded to a mechanical screen or leaf. The filtration media is chemically inert and contain a silica skeleton. A pre-coat filter removes suspended solids, contaminants and other particulate matter; to build a pre-coat primary filter medium layer to be deposited on the basic screen. The correct cake buildup is essential for optimum filtration results.

Sometimes pre-coat filter performance is not up to a satisfactory level due to the quality of cake build up. Gas plants are putting extra efforts to maintain gas treatment units to control amine quality.
Application of Reservoir Navigation with Boundaries Detecting Technologies in Lufeng Oilfield, South China Sea
Authors: Yiling Hao , Shuquan Xiong , Yiming Wu , Yongjun Fang , Chuyin Li
Published: May 2016

Reservoir Navigation with Boundaries Detecting Technologies, Baker Hughes AziTrak™ azimuthal navigation can achieve maximum standoff to oil/water Contact and minimum standoff to shale roof, increase exposure to reserves and identify future opportunities. CNOOC, one of China's major operators recently used this servicesdrilled 7 wells with 3570 m lateral section in the Early Miocene Zhujiang sandstone formation while maintaining a challenging distance of 0.8 m from the roof of the formation and safe standoff above bottom/boundary water.

"The ability to drill accurately within the zone was impressive, and the ability to also drill it fast was remarkable, with exact wellbore placement, you can extract more value from mature field" said the client's management representative. In the demonstration effect of this field, more and more fields of CNOOC are taking the Reservoir Navigation with Boundaries Detecting Technologies to facilitate simplified reservoir navigation decisions for increasing efficiency, saving rig time with early oil-water contact-zone detection, driving maximized hydrocarbon recovery through precise wellbore placement. This paper will be focusing on above cases to study.
Renovation of Old Well Logs Run in Boreholes Drilled with Oil-Base Mud
Authors: Elkewidy Tarek Ibrahim
Published: May 2016

The problem of correcting for oil-base mud filtrate invasion has been resolved using modern well logging technology of tools and interpretation techniques. However, many well logs from old wells remain uncorrected. Old interpretation assumed no oil base mud filtrate invasion. The consequences may vary between unnecessarily perforating a water-bearing zone to even worse by completely by-passing a hydrocarbon formation.

Lau et al. (1989) developed a correction for oil-base mud effects on neutron and density logs, however the standard formation evaluation techniques from the Dual Induction Resistivity Log, DIL, relies on knowledge of the resistivity of the invaded zone, Rxo. Since no electrode-type tool can work in oil base mud to measure Rxo, a synthetically derived Rxo from the Electromagnetic Propagation Time (EPT) or the Thermal Neutron Decay time (TDT) logs is used. In the absence of these unconventional EPT or TDT logs, interpretation is performed assuming no oil mud invasion and the deep induction resistivity, RID, is reading the true formation resistivity, Rt. However, it has been proven that oil mud filtrate will invade the formation sometimes to a diameter greater than 120 inches. This invasion will greatly affect Rt masking the hydrocarbon potential of the reservoir to the extent that a water zone may appear as hydrocarbon-bearing.

Without proper consideration to the oil-base environment surrounding the logging tools, essential petrophysical parameters such as true formation porosity and resistivity cannot be accurately measured. Techniques and concepts such as crossplotting log j versus log Rt or log Rxo, BVW, shale zonation index, fracture partitioning coefficient, etc. may not be all conducted. Evaluation of properties such as Sw, Sxo, Smo, m, n, jma, jf, FII, etc. will not be reliable. Consequently, zonation of a heterogeneous reservoir into its hydraulic units cannot be accomplished.

In this study, a new practical and cost effective technique is introduced to correctly evaluate formations with deep oil-base mud filtrate invasion of old well logs in the absence of EPT, TDT, logs, i.e. without a prior knowledge of Rxo or Rw. This will allow characterization of old reservoirs drilled with oil-base muds using the available old conventional well logs without the need for running new expensive well logs.
Preliminary Analysis of Diagenetic Effects on Basin Scale Overpressure Dynamics
Authors: Scrofani G. , Ruffo P. , Porta G. , Riva M. , Lever V. , Scotti A. , Imperiali I.
Published: May 2016

This study introduces a diagenetic modeling approach which is then applied to a simple one-dimensional scenario with an alternation of sandstone and shale layers. A key focus of the work is the analysis of the role of critical parameters that may drive pressure and overpressure dynamics in a basin. Due to its one-dimensional nature, the modeling technique presented can be currently applied as a Quality Control (QC) tool to assess the occurrence of diagenetic effects that might affect pressure evolution to assist in improving forecasting of overpressures in a new well in the same area or under similar geological settings. Coupling of hydro-geochemical and mechanical processes with the evolution of temperature enables one to model the effect of basin scale temperature-activated reactions on diagenetic scenarios. The resulting set of partial differential equations includes parameters whose values are always affected by high uncertainty. We provide uncertainty quantification (UQ) of the compaction process through a Global Sensitivity Analysis (GSA) of the system response following incomplete knowledge of a set of model parameters. The model response is approximated through a polynomial chaos expansion of the system dynamics. This decomposition provides (a) a GSA based on Sobol indices, and (b) a meta-model of the system that can then be adopted to perform multiple Monte Carlo realizations of the diagenetic process at an affordable computational time. Our results allow to (i) investigate the effect of parametric uncertainty on the system states, and (ii) perform robust parameter calibration within an inverse modeling framework. This work does not disclose significant data from the field or computer work; it contributes to improve our understanding and modeling of diagenesis of sandstones and shales and basin overpressure evolution.
A Modified Archie Relationship - A Novel Approach to Evaluate Carbonate Reservoirs with Regard to Fracture and Isolated Vuggy Porosityfor Sw=1
Authors: Muller-Huber E. , Schon J.
Published: May 2016

Carbonate rocks hosting major proportions of the world's hydrocarbons are characterized by intricate pore systems encompassing different pore scales, shapes and interconnections resulting both from their organic origin as well as different diagenetic processes (e.g. dolomitization, fracturing, leaching, cementation or recrystallization). Apart from interparticle pore space composed of micro-, meso- and macropores, there are also separate and connected vugs (e.g. fractures), influencing important reservoir parameters such as total and effective porosity or permeability. Therefore profound knowledge of the impact of pore types and interconnections on log data has to be acquired in order to ensure accurate evaluation with respect to porosity. Particularly regarding electrical properties and Archie's relationship - having been established for clean rocks and connecting formation resistivity factor F and total porosity - a special modification in carbonates with regard to their complex pore systems is required. Thus a petrophysical database including resistivity and porosity data of a range of carbonate rocks with various pore types (interparticle and vuggy, both separate and connected) needs to be established. The analysis of the database leads to a modified Archie relationship taking account of the effect of separate vugs and fractures on electrical current flow. This novel modification allows a first step towards porosity partitioning in a water-saturated carbonate formation into proportions that are isolated or accessible for electrical current flow and thus also for hydraulic fluid flow - one of the most important features with regard to producibility and recovery. A set of log data from a sample well is presented to apply and test this new approach on carbonates with challenging pore space characteristics. This novel modification of Archie's equation may prove beneficial to fields of research related to reservoir properties in complex carbonate reservoirs.
Identification of Favorable CBM Area Based on a Two-Tier of System
Authors: Feng Lijun , Yuan Zhengrong , Kleverlaan Martijn , Ghosh Sanjoy
Published: May 2016

Coal bed methane is formed during the coalification stages and stored in coal seams, however the preservation of methane within the seams from the time of formation to present day predominantly depends on the evolution of local geological structure and the associated hydrogeological conditions following the coalification stage. Poor trapping conditions are more likely to result in an unfavorable CBM area. In this paper the evolution of geological structure and hydrogeological conditions of the North Shilou (NSL) CBM block is analyzed using an integrated approach. A two-tier system is developed to identify favorable CBM areas: Tier one considers geological structure and hydrogeological conditions; and Tier two the CBM reservoir properties. Two areas with different resource potential have been identified in the NSL block using this approach. One is characterized by higher gas content and saturation and limited groundwater recharge, where lithological trapping is predominant. The other, potentially less favorable, is characterized by lower gas content and saturation along with active groundwater recharge, where hydrodynamic trapping is predominant. The approach is able to explain reasonably the performance of the existing production wells in NSL block to date.
Optimal Fracture Spacing of a Hydraulically Fractured Horizontal Wellbore to Induce Complex Fractures in a Reservoir Under High In-Situ Stress Anisotropy
Authors: Jo Hyunil
Published: May 2016

It has been generally accepted that creating complex fracture networks by hydraulic fracturing is one of the most efficient ways to produce gas from shale gas reservoirs. Although several factors affect development of complex fracture networks, the in-situ stress anisotropy (i.e. maximum in-situ horizontal stress - minimum in-situ horizontal stress) is the most significant factor. Low in-situ stress anisotropy increases the chance of creating complex fracture networks by hydraulic fracturing while high in-situ stress anisotropy reduces the likelihood of complex fracturing.

In order to compensate for high in-situ stress anisotropy without drilling additional wellbores, M.Y. Soliman suggested using a fracturing method referred to as the Texas Two Step Method (TTSM). The method rearranges the sequence of fracturing stages to make use of the induced stress contrast caused by the net fracturing pressure. In this paper, the author has reviewed previously published assumptions with regard to the above method, and has concluded that certain assumptions may not be realistic, e.g., the interaction among propagating fractures were not thoroughly considered.

To analyze the effectiveness of TTSM, this research has developed numerical codes using the Discontinuous Displacement Method (DDM). Through this research, certain critical characteristics related to fracture geometries are shown to be affected through interaction among multiple hydraulic fractures. The effect of these critical characteristics on the TTSM predictions for optimal fracture spacing of multistage fracturing operations is presented.

From the results, it is concluded that curved fractures can increase or reduce the stress contrast induced by the net fracturing pressure, depending on the shape of the curved fractures. This paper further introduces a simple and general formula to calculate the optimal fracture spacing for TTSM.
The Liwan Gas Project: A Case Study of South China Sea Deepwater Drilling Campaign
Authors: Triolo David , Mosness Tracy , Habib Rana Khalid
Published: May 2016

In September 2006, Husky Energy discovered the Liwan gas reservoir in its South China Sea Block 29/26. A 6th generation, deep water semi-submersible was contracted and subsequently drilled 26 deep water wells (700 - 1600 m water depth) consisting of 10 exploration, 10 appraisal and 6 development wells, tested 6 wells between November 2008 and November 2011. The exploration program discovered several additional sandstone, gas-bearing reservoirs two of which will also be commercialized. During the 1,011 days of drilling and testing activity, the rig and supporting onshore teams did not incur a lost time accident. The rig team drilled 61,593 m of hole below the mudline and ran the associated strings of casing. Non-productive time consumed 265 days (26.2%) consisting of 65 days waiting on weather, 147 days of rig repair, and 53 days of other unscheduled events.
Laboratory Study and Field Application of Fiber-Based Fracture Reorientation Technology
Authors: Yang Shi , Fujian Zhou , Xianyou Yang , Xiongfei Liu , Shengjiang Lian , Xiangdong Li
Published: May 2016

When implement fracture treatment in fractured reservoir or wells had been fractured before, new fractures need to be formed in a beneficial position so that the reservoir can be connected with wellbore effectively. In fiber-based fracture reorientation technology, degradable fiber is utilized as diversion agent to block up original fractures, and divert the fluid to open new fractures. To validate this reorientation effect, this paper designs the physical simulation experiment with big size samples (300mm×300mm×300mm), and real tri-axial stress simulation system. This system can apply stress on the rock from 3 different directions during the fracturing physical simulation experiment.

The results indicate that: multi-fracture system formed in every rock sample simulated with fiber-based fracture reorientation technology when different tri-axial stress applied on the samples. Fiber-based fluid can block up the original fractures effectively and open new fractures in different directions. That is to say, this technology can improve SRV (stimulated reservoir volume) significantly.

Field test and fracture monitoring with tracer had been conducted. The tracer signature shows that multiple fractures have been created after treated by fiber-based fracture reorientation technology.

Fiber-based fracture reorientation technology is an effective treatment to create multiple fractures, and it is a prominent stimulation method for the fractured reservoir and the wells need to be re-fractured.
Silurian Source Rock System in Time and Space
Authors: Spaak Pieter
Published: May 2016

With the rising interest in unconventional oil and gas plays, the need for better understanding and detailed reconstructions of source rock systems becomes even more important than for conventional plays. One of the Series in which these occur in large numbers is the Lower Silurian. In this presentation, the variation in (depositional) setting for the Silurian source rocks will be illustrated, through a careful reconstruction of the Silurian flood in time and space. Although these source beds typically occur at or near the base of Silurian, some are clearly linked with oceanic upwelling, some accumulated in relatively confined foreland basin settings whereas others were formed on a broad but tectonically and glacially modified Gondwana shelf. This contribution illustrates that the depositional, temporal and 'tectonic' variations for one of the 'so-called' global source rocks events can be considerable. Generalizations and un-calibrated use of models, analogues and properties should not be made.
AVO Research on Coalbed Methane Reservoirs in East Ordos Basin
Authors: Zhang Tieqiang , Sun Pengyuan , Qian Zhongping , Ma Guangkai
Published: May 2016

DESCRIPTION:

In east Ordos basin, there are plenty of coalbed methane (CBM) resources. However, the coalbeds are of strong heterogeneity due to laterally variant thickness and gas contents. Consequently, the heterogeneity gives rise to the great challenges for fine reservoir prediction and evaluation in seismic exploration. For the purpose of applying AVO to CBM prediction, in this paper, combining with geological and geophysical characteristics of CBM reservoirs NO. 5 coal seams from drilling, logging and the relationship between elastic parameters and gas contents in the lab, we established a set of thin coalbed models with different thickness and gas contents to model AVO using reflectivity method. Subsequently, AVO responses to gas contents and thickness of CBM reservoir are systematically investigated.

APPLICATIONS:

Our researches are theoretical discussion about the relationships between AVO responses and coalbed thickness and gas contents. These relationships can be applied to exploration of CBM reservoirs in practice.