bluuebunny/crossref_metadata_2025 huggingface dataset:
Seismic Guided Drilling: Near Real Time 3D Updating of Subsurface Images and Pore Pressure Model
Authors: Peng Chuck , Dai John , Yang Sherman
Published: May 2016

Seismic guided drilling (SGD) is a workflow that uses drilling information from a well being drilled and existing surface seismic data plus offset well information, to recalibrate and update the existing 3D earth model, including seismic image, pore pressure, fracture gradient, and geological hazards in order to reduce drilling uncertainty and mitigate drilling risk ahead of bit.

The modern practices in drilling heavily rely on the predrill earth models. The predrill models often are not precise due to the inherent non-uniqueness in our remote sensing techniques. While LWD/SWD and WL provide useful information along the borehole, they offer little understanding about the rock property ahead of bit. SGD is such a technology that constantly improves the 3D earth model ahead of the bit through the integration of current well measurements with existing surface seismic data, with a turnaround time on the order of 24hours. It not only corrects the model error behind the bit but also improve predictions ahead of the bit.

The lack of adequate technologies, measurements, and turnaround time limitations, has made this type of optimum utilization/integration of seismic data and well data impractical until now. Recent developments in model building, rapid and accurate imaging technologies, and the availability of new well measurements, aided with modern engineering and computation, have made this optimum combination a reality. SGD has been used in several high-profile deep water HPHT wells worldwide with considerable successes. The technology is especially valuable in areas of low exploration activity or high geological complexity.

The paper focuses on illustrating the concept of SGD technology and presenting a field example in the Gulf of Mexico, USA.
Determining Coefficient of Quadratic Term in Forchheimer Equation
Authors: Ling Kegang , He Jun , Wu Xingru , Shen Zheng
Published: May 2016

Forchheimer equation takes non-Darcy flow effect into account in the event of high flow velocity in porous media. Its application requires both permeability, which is in linear term, and Beta factor, which is in quadratic term. Permeability and Beta factor are determined by rock type, textural of rock, effective porosity, pore throat size, geometry of the pore, and connection and distribution of pores. Beta factor comes into play when the fluid flow rate is high and the flow rate deviates from Darcy's law. Non-Darcy flow is described by Forchheimer equation. Usually the coefficient of non-Darcy flow term is hard to be determined. Existing approaches are core measurement and empirical correlations. To the best of our knowledge there is notheoretical equation available. To get an accurate estimation of flow rate or pressure drop in the reservoir, we need a method that has solid theoretical basis. The deficiency triggered our study.

Starting from multiple-capillary tubes concept, we derived a rigorous relationship between pores geometry and pressure drop required for fluid flow through the pores. Through this correlation pressure drop can be calculated from known pores geometry. Since pores geometry can be often obtained from lab experiment or well logging, the new correlation also provides a unique approach to quantify the coefficient of quadratic term in Forchheimer equation.

In this study we developed a governing equation through a rigorous theoretical derivation. With this equation the non-Darcy flow coefficient in Forchheimer equation can be calculated. The required input data for the new equation are readily obtained from well log interpretation. The new equation is a powerful tool in the event of no experimental measured non-Darcy flow coefficient available. It eliminates the errors or the arbitrary content in the empirical correlations.
Integrating an LNG Plant with an Unconventional Gas Supply
Authors: Langley Chris , Spaander Adriaan
Published: May 2016

Arrow Energy is a JV company based in Brisbane, Australia, that is owned50/50 by the Shell group and PetroChina (a subsidiary of CNPC). Arrow is planning to develop its tenement holdings of Coal Seam Gas (CSG) in the Surat and Bowen Basins of central Queensland. The CSG will be produced at very low pressures from shallow wells, gathered and compressed into two 500 km trunk-lines for delivery to a two train LNG plant, with each train sized at 4.0mtpa capacity. The LNG plant will be located on Curtis Island, opposite Gladstone harbour, in Queensland.

CSG is classed as "unconventional" gas; this is the first time that Shell or PetroChina have designed an LNG plant with an unconventional gas feed. The paper discusses the unique aspects of integrating an LNG plant with this unconventional gas feed.

The main topics covered in this paper are:Implications of CSG composition for LNG plant design,Implications of CSG ramp-up for LNG plant design,Optimising the Availability of the Integrated system, and,The use of novel design and new technology approaches in the LNG plant in order to reduce costs.
Hydraulic Fracturing Candidate-Well Selection by Interval Type-2 Fuzzy Set and System
Authors: Zoveidavianpoor Mansoor , Samsuri Ariffin , Shadizadeh Seyed Reza
Published: May 2016

Selecting a target formation(s) among a vast numbers of zones/sub-layers within huge numbers of hydrocarbon producing wells in a reservoir, is considered a difficult task, particularly if the selection goes through a group of parameters having different attributes and features; such as geological aspect, reservoir and fluid characteristics, etc. The trend of candidate-well selection (CWS) process for Hydraulic Fracturing (HF) had recognized to be complex, nonlinear, un-equilibrium, and adherent with uncertainty. Interval Type-2 Fuzzy Logic and Systems (IT2-FLSs) are very useful in circumstances where it is difficult to determine an exact membership function (MF) for a Fuzzy Set (FS); hence they are very effective for dealing with uncertainties. Classical FLS which called T1-FLS is not capable of fully capturing the linguistic and numerical uncertainties in the terms used and the inconsistency of the expert's decision-making. Therefore, the need arises to use a method that could handle uncertainties. The procedure of applying this novel study in the area of HF CWS, will have illustrated through a case study in a carbonate reservoir. The utilization of a modern and right problem-solving tool such as T2-FSS should be considered a great concern to the petroleum industry. Although sizeable clarity has been achieved in this area, no conceptualization such as dealing with uncertainty, has yet answered by the previous studies. New requirements force the previous methods to advance and novel techniques expected to meet the requirements and remove the existing weakness. In highlighting this need, the question has been answered about why IT2-FLSs should be used in this study. Also, its advantages over T1-FLS will be illustrated. This paper critically assesses the importance of the proposed methodology to develop a reliable model of HF CWS. This investigation is the first research which applied such a cutting-edge approach and tries to fill the gap between recent developments in uncertainty management through utilization of IT2-FLSs in HF candidate-well selection.
Drilling of Multilateral Wells Aided with Geochemical Analysis
Authors: EL Gezeeri Taher , Ismail Abdul Aziz , Al-Anezi Khalaf , Al Jeaan Monirah , Silambuchlvan Jeevan Kumar , Padhy G.S. , Wasnik Atul , Al Shoeibi Ahmed
Published: May 2016

This paper describes the utilization of Real-Time geochemical analysis to support geosteering of a smart multi-lateral well, located in one of the highest flow potential areas in Kuwait. The Burgan reservoir consists of vertically stacked channel sands along with a fault network connected to the aquifer and contains highly viscous reservoir fluid. This drastically enhances the water mobility, and results in severe premature water breakthrough. Hence, leaves zones of by-passed oil. For optimum reservoir characterization, it was essential to integrate all reservoir-related data from macro to micro scale. X-ray Fluorescence elemental data collected from offset cores were used to predict key rock attributes and calibrated with standard petrophysical logs. The scope was constructing predictive models for the following properties:lithological variations which cannot be captured by other LWD toolsdetailed mineralogy to determine the diagenetic overprintdepositional environment of different Burgan sand facies.

XRF elemental analysis while drilling was used to improve borehole positioning, and identify faults in correlation with Image logs. Nature of the fractures/faults, contributing to porosity and communicating with the aquifer, was inferred from XRF-obtained elemental markers. The integrated approach has resulted in successful geosteering and placing the well with maximum reservoir contact. Moreover, XRF elemental markers have been utilized for isolation of faulted and lower reservoir quality zones, splitting up of horizontal sections and optimization nozzle sizes of the ICDs and hence an optimized Smart completion design. X-ray fluorescence analysis on cuttings in Real-Time provides lithological information otherwise not available while drilling. It gives proxies contributing to the identification of faults and reservoir intervals in an otherwise homogeneous sequence. It helps designing the completion string, isolating sections of low quality or potentially producing water.
Optimizing Dehydrators Operation Using Dynamic Adsorption Time
Authors: Almakrami Eisa A , Gadi Amr A.
Published: May 2016

Molecular sieve is a solid desiccant widely used in gas plants for dehydrating wet process gases. Compared to other desiccants, molecular sieve can reduce water content in the outlet gas to less than 0.1 ppmv. This is a must requirement for conditioning feed gas to cryogenic applications. On the other hand, Molecular Sieve is generally more expensive and energy exhaustive.

This paper describes the successful implementation of the Dynamic Adsorption Time Control Module for dehydrators in natural gas liquid (NGL) recovery trains at Saudi Aramco's Hawiyah NGL Recovery Plant (HNGLP). The module optimally utilizes the available dehydrators capacity by applying dynamic adsorption time for dehydrators based on available desiccant capacity, processed gas flow and incoming water content. As a result of this optimized utilization, the frequency of regeneration cycles is reduced. This results in extended desiccant lifetime, and reduced lost revenue and energy consumption over the desiccant life cycle.
Useful Recycling and Safe Disposal Technology of Waste Oil Based Drilling Fluids and Its Application
Authors: Xie Shuixiang , Deng Hao , Wang Rongsha , Yue Yong , Wu Baichun , Liu Guanquan , Xu Yu
Published: May 2016

Waste oil-based drilling fluids are hazardous wastes containing oil, heavy-metal and organic pollutants. However, the common treatment methods at home and abroad these methods not only waste many useful resources (because the oil is discarded rather than recovered) but also increase the pro-environment cost of oil companies. This paper develops useful recycling and safe disposal technology of waste oil-based drilling fluids from the perspective of utility, efficiency and economy, which not only recycle useful oil but also reuse and dispose of the rest of mud and waste drilling fluids. The rate of recovery is greater than 90%, and the quality of the recycled oil is very good and meets the requirement of -10 # diesel of cars in GB/T 19147-2003. The concentrations of oil, COD (chemical oxygen demand) and heavy metals in liquid of the processed mud are lower than the secondary standard number in GB8978-1996. The treated wastewater meets the requirements of sewage comprehensive emission.
Equation for Oil and Gas Two-Phase Flow into Vertical Well - A Theoretical Derivation
Authors: Ling Kegang , He Jun
Published: May 2016

Generally reservoirs are classified into five categories according to the reservoir fluids. Single phase flow in reservoir is expected during the production life for wet gas and dry gas reservoirs. But for black oil, volatile oil, and gas condensate reservoirs, two-phase flow will occur after pressure declines to saturated pressure and the second phase saturation reaches the critical saturation. Theoretical derivation of single-phase flow into vertical well had been done by former investigators. The solutions to different boundaries at different flow status were provided through different simplifications and assumptions. These solutions provide powerful tools for reservoir study. But when it comes to oil and gas two-phase flow, they cannot be applied. To the best of our knowledge there is no rigorous and theoretical derivation for the oil and gas two-phase flow into the well.

In this study, rigorous and theoretical derivation of oil and gas two-phase flows from reservoir into the well was conducted. Starting from the famousDarcy's equation, the flows of oil and gas are controlled by the rock/fluid properties, pressure, and temperature condition. The continuity equation was applied. With the combination of equations of state and the concept of compressibility, the governing equation of oil and gas two-phase flow was constructed. Even numerical approach is required to solve the equation to get gas and oil flow rates, the new equation still has its significance due to its theoretical and rigorous derivation. It can be used as a unique tool to solve the saturated oil and gas condensate reservoirs that experience two-phase flows. The proposed equation addresses the rigorous derivation of two-phase flow in a radial reservoir. It eliminates the uncertainty in the empirical equation and has the advantage of quickness and simplicity comparing with reservoir simulation method. It becomes a powerful tool for petroleum engineers.
Upstream Stranded Raw Gas Management as Compressed Natural Gas (CNG)
Authors: Economides Michael J. , Wang Xiuli , Colafemmina Francesco , Tomaselli Vanni Neri
Published: May 2016

Marine compressed natural gas (CNG) has been considered in the past as a means of natural gas transportation but proved to be a non-starter for a number of reasons including long distances or large volumes of gas when compared with liquefied natural gas (LNG). However, marine CNG still figures economically attractive over shorter voyages (up to ~4,000km) and medium volumes of gas. Recent advances in containment systems are poised to provide marine CNG with the best opportunity to be resurrected as a major enabler of new and previously stranded hydrocarbons by becoming an important optimization tool to petroleum well performance.

Almost half of offshore natural gas, SEC-type, reserves are considered" stranded" because of the high unit technical cost to harness natural gas in remote locations involving deep-water and/or pre-salt basins, and the lack of are liable and commercially viable market for the natural gas. Most of them do not contain enough gas to justify their own gas transmission solution, floating or onshore LNG production. Furthermore, inoperable gas affects oil production in many adverse ways from the logistics of handling and facilities capacity to the cost of the treatment. Marine CNG used as a wellhead fluid shuttling service for raw gas can generate significant monetary benefits for an operator attributable directly to the new technology and innovative application. Gas viewed like this is no longer a mid-stream product in need of further processing prior to sale, but becomes a potential upstream saleable product.

We present here the new technology emphasizing the containment system manufactured with composite materials that are far lighter than metal and yet can withstand the 200-atmosphere pressure and corrosion from hostile raw gas composition straight out of the primary separator. CNG cargo containment system produced with composite materials can reduce overall steel weight by 50–80% and can operate with pressures ranging from 150 to 250 bars, sufficient to accommodate a wide range of gas-oil-ratios without the need of refrigeration.
Paleogeomorphology Analysis and its Application in Exploration and Production of Karstic Ordovician Carbonate
Authors: Yang Haijun , Tong Yanming , Deng Wensi , Yang Pin , Pan Wenqing , Chen Lixin , Lei Xue , Wu Chuan
Published: May 2016

Introduction

The Ordovician carbonate karst reservoir which is usually buried 5000m deep is an increasingly important target for oil exploration and production in Tarim Basin, West China. The paleogeomorphology of the top of the Ordoviciancarbonate directly controls reservoir development and hydrocarbon accumulation, so detailed characterization of karst paleogeomorphology is one of the keysteps to identify reservoir development rules which will lead to more efficient exploration and production activities in the study area.

This paper presents an example study on carbonate karst paleogeomorphology in Tarim Basin. Also, its significance to exploration and production activities has been discussed.
Integrating True Valve Performance into Production System Analysis Based Gas Lift Design and Troubleshooting for Dukhan Field, Qatar
Authors: Singh Sanjay K. , Hall James W. , Khalil Eraky , Al-Marri Balsam , Al-Abdulla Reem
Published: May 2016

Qatar Petroleum's Dukhan field uses gas lift to produce oil wells that cannot sustain natural flow because of reservoir pressure decline or rising water-cut. The increasing number of wells on gas lift has made the effectiveness of gas lift design and troubleshooting a key factor to achieving crude oil production targets. Until the present day production system analysis methods were used for gas lift design and troubleshooting. This was found to be inadequate in several cases to achieve an optimum design or to troubleshoot problems successfully. To resolve such inadequacy, a new approach has recently been applied that makes use of the VPCTM (Valve Performance Clearinghouse) database. The VPCTM database provides tested or true performance data for gas lift valves. The new approach integrates well performance from production system analysis and true valve performance from the VPCTM database into an integrated system performance tool. Sensitivity analysis of the integrated system is then performed with a set of well conditions and valve parameters for gas lift design or troubleshooting. The paper focuses on the intricacies of the approach and presents a typical field example of its application. Application of this approach has enabled effective gas lift design and troubleshooting, unlocked incremental oil potential at negligible cost and extended the producing life of wells.
Simulation of Chemical Interaction of Injected CO2 and Carbonic Acid Based on Laboratory Tests in 3D Coupled Geomechanical Modelling
Authors: Masoudi Rahim , Abd Jalil Mohd Azran , Tan Chee Phuat , Press David , Keller John , Anis Leo , Darman Nasir , Othman Mohamad
Published: May 2016

The M4 field is located in the North of the Central Luconia Province in the Sarawak Basin, East Malaysia. The reservoir is approximately 2000 m below sea-level where the water depth is approximately 120m. A study for CO2 geological storage has been carried out to address the feasibility of injecting and storing CO2 in the M4 depleted carbonate gas reservoir using 3D coupled geomechanical modeling. The water level in the reservoir has risen close to the cap-rock which implies a strong aquifer.

Laboratory tests were carried out on core samples before and after injection of a CO2 saturated brine solution, and the results were used in the determination of material property strength and elastic property degradation due to acid-carbonate interaction. Triaxial compression tests on carbonate samples from three different depths at the peak loading stage of the tests for different confining pressures were performed. The effects of CO2 saturation on UCS, Young's modulus and Poisson's ratio were determined. The permeability measurements from the pore volume compressibility tests and permeability measurements obtained during the measurements of petrophysical properties were used to evaluate the effects of acid-carbonate interactions.

The 3D geomechanical model coupled the reservoir pressures derived from a dynamic model with a stress simulator in order to calculate changes in effective stress and volumetric strain within the 3D model. The derived changes in volumetric strain were related to a change in porosity and permeability which were then passed back to the dynamic model in a staggered solution scheme. At each "stress step" in the solution process, a further modification was made to geomechanical material properties due to the increased CO2 saturation from injection. The material parameter modifications were based on the results of the laboratory tests above. In this way, the material property degradation due to CO2 injection was accounted for during the coupled reservoir geomechanical simulations.

The paper discusses the results of these tests and the derived variation of material permeability, elasticity and strength parameters with CO2 saturation for subsequent input to the coupled geomechanical solution scheme. In this way, the potential risk due to the chemical interaction from CO2 injection could be evaluated quantitatively.
Casing Failure Mechanism and Characterization under HPHT Conditions in South Texas
Authors: Yuan Zhaoguang , Schubert Jerome , Esteban Urdaneta Carbonell , Chantose Prasongsit , Teodoriu Catalin
Published: May 2016

Casing failure probability is high in Ann Mag Field, South Texas due to the high pressure high temperature operational environment. The formation sands are over-pressured where the pore pressure ranges from 0.85 to 0.93 psi/ft. Casing damage has been experienced in over 11 wells from 18 that have been drilled in the area, near 61% of total wells were damaged during their production life.

Casing failure may be caused by formation shear failure, formation compressive failure, casing tension failure, casing collapse or fault activation. Casing buckling is not considered in the study because cement bond logging shows that the cement sheath is good. Triaxial tests were carried out to measure formation mechanical properties that were used for reservoir compaction, fault activation and formation failure analysis. The Mohr-Coulomb failure criterion was applied to study the formation failure and the minimum pore pressure required to activate the fault. The finite element methods were used to analyze the casing tension failure caused by reservoir compaction.

According to the formation shear failure analysis, the minimum allowable pore pressure around the casing is around 2,000 psi. In the study of fault activation, for shale formation, at the internal friction coefficient of 0.51, the probability that the normal fault can be activated is very high. The maximum drawdown and depletion were calculated based on potential casing failure types. In the plot of workability operational limits, shale formation has narrower safe zone than the sand formation. Recommendations for drilling and production were made to increase the well service life and improve the gas recovery.

This paper presents the casing failure mechanism and characterization under HPHT conditions in south Texas that can be prevented in the future wells and provides workability operational limits for different formations.
QC of the Reservoir Model Using Seismic, Well Logging and Petrophysical Data
Authors: He Weisheng , Ling Yun , Guo Xiangyu
Published: May 2016

For the oil fields in the mature stage, it is most important to find the remaining oil in the reservoir. A typical method to predict the remaining oil is fluid flow simulation based on the geological model generated with all the available data. The agreement between the reservoir simulation model and the production data is usually used to evaluate the quality of the simulation model. Reservoir engineers often find that more than one simulation model could match production data, which is due to the limitation of the production data, only available at the well location. However, the seismic data are available in 3D. A method of quality control of the reservoir model using 3D seismic, well logging and petrophysical data is proposed in this paper. The proposed method is applied to a pilot test in a heavy oilfield. Using the well logging data and seismic horizons in the study area, a geologic model was generated and upscaled to a simulation model. With this model, reservoir simulation was run to simulate the reservoir changes over the time. Using the petrophysical data, the synthetic seismic data of reservoir model were calculated. And then the synthetic seismic data were compared with the observed seismic to evaluate the reliability of the reservoir model. The application shows that the introduced method can be used to quantitatively evaluate the reservoir model and its outcome can also aid us to update the reservoir model. The updated model is proven to be more reasonable.
Derisking of Unconventional Gas Opportunities: Application of Basin Modelling
Authors: Keym Matthias , Dieckmann Volker , Meuric Olivier , Idiz Erdem
Published: May 2016

Unconventional Liquid Rich Shale (LRS) and shale gas (SG) plays are self-charged continuous systems relying on their indigenous organic matter as the source of hydrocarbons. The residual pore space of fine-grained organic rich sediments themselves or similarly tight deposits in their close vicinity act as the reservoirs. Pressure (P) and temperature (T) can significantly increase during burial of the sediments and can likewise undergo a substantial instant P but time-deferred T decrease during erosion and uplift. These changes in P and T strongly influence the phase behaviour of the generated and trapped hydrocarbons (HC), thereby affecting the retention capacity of the source rock, the HC flow properties, potential migration routes, and the predicted HC volumes initially in place (GIIP/OIIP). Shell's integrated Cauldron Shale Gas Simulator calculates resource density on a regional to basin scale, typically during the opportunity identification and screening phase of a project. Informed decision-making in exploring for unconventional opportunities relies on the integration of all available (i.e., sometimes scarce) data and their associated uncertainties for basin scale physical elements and processes into a working geologic model.
Strain Based Design and Material Selection Technology for Thermal well Casing
Authors: Lihong Han , Jianjun Wang , Hang Wang , Changyi Qin , Yaorong Feng , Bin Xie , Xuelu Zhang , Zhihua Tian
Published: May 2016

Field investigation and failure analysis on casing damage were conducted for cyclic steam stimulation thermal wells in Xinjiang oil-field of China. Evaluation demonstrated that stress-based casing design only meet the requirements of drilling and completing operation, but could not accommodate sufficient security for cyclic thermal production. Although casing failure seldom appeared during drilling and completing, lots of its failures happened within the following production stage. These results indicated that the service environment during this production is the dominant factor affecting casing design and material selection.

Failure analysis displayed that there are several typical modes, including deformation, necking, shear, crack and connection parting. These typical modes revealed that those casing experienced obvious plastic deformation during production. Accordingly, strain-based design is proposed in which characteristics of deformation behaviors are taken into account, such as plastic deformation, hardening, creep, stress relaxation, bauschinger effect and strain fatigue limit. Two criterions were determined for this design according to plastic capacity and strain fatigue limit of casing material, respectively. Moreover, one of these criterions had been verified through 8 wells experiments after three thermal cycles.

Strain-based design aims to present sufficient axial plasticity capacity beyond elastic limit, before ultimate necking and tensile fracture. It is necessary to consider attached measures for integrity of thermal wells. For thread connection, sufficient sealability is recommended to prevent steam leakage, otherwise which could greatly promote shale's expanding and then result in shear failure in casing. As for the pipe ends, external upset or additional hardening process is suggested to apply to maintain the integrity of thread connection area.
Prediction and Reduction of Perforating Gunshock Loads
Authors: Baumann Carlos , Barnard Keith , Anbao Lu , Williams Harvey , Fuxiang Zhang , Xiangtong Yang , Jianxin Peng
Published: May 2016

Most wells and particularly high-pressure wells are susceptible to gunshock damage when they are perforated with inappropriate gun systems and/or under suboptimal conditions. This paper presents a simulation methodology to predict gunshock loads for tubing-conveyed and wireline-conveyed perforating jobs.

When planning perforating jobs in high-pressure wells, engineers strive to minimize the risk of equipment damage due to gunshock loads. The methodology described here helps engineers to identify perforating jobs with significant risk of gunshock related damaged, such as bent tubing and unset or otherwise damaged packers. When predicted gunshock loads are larger than the admissible loads, changes to the perforating equipment or job execution parameters are sought to reduce gunshock loads. This methodology enables completion engineers to evaluate the sensitivity of gunshock loads to changes in gun type, charge type, shot density and distribution, tubing size and length, number of shock absorbers, rathole length, and placement/setting of packers, among others.

Fast gauge pressure data from perforating jobs shows that when model specifications are representative of the actual perforating jobs, the predicted wellbore pressure transients are accurate both in magnitude and time. Peak sustained pressure amplitudes at the gauges are on average within 10% of simulated values.

With the methodology presented in this paper, engineers can evaluate perforating job designs in a short time, and they can optimize perforating jobs by reducing gunshock loads and equipment costs. The ability to predict and reduce gunshock loads and its associated damage is very important because of the high cost associated with most wells, particularly high-pressure wells. With the software presented in this paper engineers can optimize well perforating designs by minimizing the risk of gunshock related damage and the associated rig time losses.
New Truck Vibrator for VSP Surveys, Extending the Frequency Bandwidth
Authors: Tulett J.R. , Dean T. , Armstrong P.N. , Lane D.
Published: May 2016

On land, the preferred seismic energy source for Vertical Seismic Profile (VSP) surveys is the seismic vibrator, a special vehicle mounted, mobile energy source. Seismic vibrators come in a variety of shapes and sizes, with truck-mounted vibrators the most common vehicle type during the early years of vibroseis surveys.

Truck-mounted vibrators are particularly useful for VSP surveys because the vehicle can be driven directly to the well site, but over the years the surface seismic industry has converted to buggy vibrators due to the buggy's excellent mobility in off-road terrains. This has left a gap in development of truck-mounted vibrators.

With petroleum exploration occurring in deeper wells, more complex sub-surface formations, and with steadily higher expectations for the results of VSP operations, there is a need for higher amplitude, and wider bandwidth seismic vibrators to provide critical geophysical information of petroleum reservoirs.
Overmature Shale Gas Storage Capacity Evaluation
Authors: Tian Hua , Zhang Shuichang , Liu Shaobo , Chen Jianping
Published: May 2016

Shale gas is generally believed to have been stored in forms of free compressed gas in open pores and cracks, as adsorbed gas on the surfaces of kerogen or clay minerals and as diffused gas stored within the solid organic matter (Bowker, 2007, Sondergeld et al., 2010). The nano-pores[1], which have a great effect on the shale gas occurrences, are the predominant pore type in the Barnett mudstones (Loucks et al., 2009). Therefore, it is important to understand the pore network and shale gas storage mechanism. This study aims to reveal the key affecting factors of pore development, and establish a shale gas prospect evaluation model as a function of pressure and temperature of overmature shale.

A set of outcrop and downhole samples were selected from the Sichuan marine basin and the Bohai bay lacustrine basin of China, and an immature shale outcrop sample from the Fushun Basin, northeastern China was used for pyrolysis experiment. A series of nano-pore description methods, such as FESEM, CO2 low pressure isotherm analysis (D-R method), N2 low pressure isotherm analysis (BET theory), Hg porosimetry were used to observe pore size, morphology, and abundance in gas shale. Methane adsorption capacity was measured use the isotherm adsorption system from TerraTek.

The N2 gas adsorption at low temperature and pressure (BET theory) (Bustin et al., 2008) showed that, with increasing pyrolysis temperature, the surface areas increase from 354 m2/kg (sample FS-300) to 3,102 m2/kg (sample FS-600) (Table 1), and pore volumes increase from 0. 6448 cc/kg (sample FS-300) to 10.89 cc/kg (sample FS-600) (Table 1; Figure 1), indicating that additional pores had developed in the solid products during the progressive pyrolysis. Pore volumes increase as the pyrolysis temperature increases, indicating that the pore volume in the organic matter can increase significantly during shale maturation (Table 1).

Scanning Electron Microscopic (SEM) observation of the pyrolysis residues indicates that with increasing pyrolysis temperature, the pores in the shale become more abundant. The sample of low-pyrolysis temperature contains fewer and relatively small pores compared with that of high- pyrolysis temperature (Figure 2). Sample "a", which was pyrolysed at 300 ?, corresponds to the low end of the hydrocarbon generation window. There are few micro-pores in the organic matter with the surface of the organic matter being relatively flat. The pore networks in Sample "b" which was pyrolysed at a higher temperature of 550? contains abundant pores developed in the organic matter, which are in sharp contrast with that in Sample "a". This is consistent with the intraparticle organic nano-pores interpreted to be of thermal maturation origin by Loucks et al. (2009) in the Barnett mudstones, where the nanopores most commonly have irregular, bubblelike, elliptical cross sections and range between 5 and 750 nm.
ALARP Demonstration in UCG Trial Production Operations (TPO) Facility Design
Authors: Kian-Hua Sim , Su-Fook Lo , Yun-Chung Liaw
Published: May 2016

This paper presents various techniques/ tools used to demonstrate the major Health, Safety and Environment (HSE) risks involved in the tight gas appraisal program, especially in designing the surface facility for the Trial Production Operation (TPO), has been reduced to As Low As Reasonably Practicable (ALARP). In the challenging environment of central Sichuan basin i.e. local hilly terrain and densely populated farm land, the paper looks at the local requirement and importance of the analysis right from the design phase for a safe and efficient operation of the TPO facility. The techniques covered include Hazard Identification (HAZID) Study, Hazard and Operability Study (HAZOP), Safety Integrity Level (SIL)/Instrumented Protective Function (IPF) study, Fire and Explosive Risk Analysis (FERA) and Fire Protection Analysis (FIREPRAN) study.

The paper covers the documentation of ALARP demonstration into a Design HSE Case. Major Accidents Hazards (MAH) in the TPO facility are identified using the Risk Assessment Matrix (RAM). A systematic and structured Hazards and Effects Management Process (HEMP) is applied in the design of the TPO facility and the risks associated with MAHs are actively and systematically reduced to ALARP. The effectiveness of all barriers and controls for each MAH are evaluated and complied with the set criteria (Bow-tie assessment). If the HEMP assessment determines that a barrier or risk management of a MAH is only partially effective, further remedial action and effort is done to close the gap. Besides, Safety Critical Elements (SCE) and their performance standards are identified and developed as a key input to the Asset Integrity Process Safety Management (AIPSM) in the operations phase.

Finally, the TPO facility design on a plot size of 70m x 70m pad was accepted for construction and trial production. Further improvement study and optimization has been ongoing including taking other unconventional gas (UCG) best practices and learning into the development planning.
Cave System Analysis - An Effective Approach to Predict Hydrocarbons in Cavernous Carbonate Reservoir
Authors: Luo Chunshu , Xue Fangjian , Deng Xinglang , Mao Qing , Yang Pin , Zeng Rui
Published: May 2016

Paleo krast caves, even deeply buried over 5000 meters, are important exploration targets in Tarim Basin west China. In seismic, large caves could be well observed as strong amplitude anomalies and are characterized as "string of beads" in legacy seismic data. They have dominated the production and reservers of the Ordovician carbonate reservoirs. Successful drilling on these targets quite depends on reliable prediction of fluid types in these karst caves. But seismic hydrocarbon detection has a high uncertainty due to the high variation in cave geometry and the low seismic resolution in deeply-buried carbonate. To improve drilling success rate, cave-system analysis approach was developed in our study as an effective approach to predict hydrocarbons in cavernous carbonate reservoir. Hundreds of paleo-caves have been seismically interpreted. Based on extending tendency of individual cave interpretation, the connections are delineated between caves forming multi-level and multi-branch cave systems through study area. These complex cave systems could be analog to the Mammoth Cave. This analog suggests that most caves in study area were connected during their development time. They are now much less connected due to sediment infilling and collapsing. Within the cave systems, the cave entrances, exits, collapses and relative high points of the cave systems are identified to provide the underpinnings for predicting cave fillings and fluid types, with the support from detailed structural mapping, paleo-topography study, production performance diagnosis, and seismic inversion/ attribute evaluation. Several hundreds of oil-bearing caves are predicted within the study area, providing the main basis for drilling plan. New drilling has led to several high productive wells after two year's unsuccessful drilling in study area.
Investigate the Distribution of Conglomerate Masses and Build the Velocity Model with Integrated Gravity, Magnetic, Electromagnetic and Seismic Data: An Example from Kuche Depression, China
Authors: Dechun Li , Zhi Zhao , Zuzhi Hu , Shujiang Yang , Haiying Liu
Published: May 2016

Conglomerate masses, which widely developed in the piedmont area of Kuche Depression, Northwestern China, seriously affect the seismic structure imaging and limit the seismic interpretation precision. As a result, in a deep reservoir well in the area, the error between the predicted reservoir depth and the real one even is up to about 1000 m. It impedes the progress of hydrocarbon development in the depression.

Gravity, magnetic and electromagnetic (EM) responses, especially EM data, are sensitive to the existence of conglomerate masses. An integrated 3D survey including gravity, magnetic and EM methods is conducted in Kuche Depression. All available geophysical data are jointed together and interpreted on an integrated interpretation platform GeoEast®. With the inverted 3D resistivity data we describe the spatial distribution of lithology and with the seismic data we give a believable structural frame interpretation. Joining the two kinds of data as well as drilling data and outcrops information, the distribution of conglomerate masses and their litholohy and lithofacies are comprehensively predicted. Subsequently, we conduct the joint inversion of gravity, magnetic, EM and seismic data and get the structural model of the intermediate and the shallow layers with which we can describe the distribution of conglomerate masses. The work improves the precision of the deep structural trap prediction. Three wells drilled subsequently shows that the maximum error between the predicted gross thickness of conglomerate masses and the real figure is only 3%. The velocity model is also built and used in the subsequent pre-stacking depth migration. It effectively helps limiting the interpretation error which results from the high-velocity horizons. The statistics of drilling data in the area shows that the general misfit of the predicted structure depth decreases from the original about 300 to 1,000 m to the present 30 to 120 m.

After the project, a complete joint interpretation system integrating gravity, magnetic, EM and seismic data is released. The system makes the interpretation of multiple geophysical data changing from the traditionally qualitative comparison job to the presently accurate description based on the multiple geophysical data. The quantitative data output from the platform can be used to build velocity model.
Hydrocarbon Accumulation Process and Exploration Potential of Shizigou-Yingdong Area, Western Qaidam Basin
Authors: Qingyang Meng , Shihu Fang , Yan Chen , Shuiwei Guan , Lili Gui , Li Yuan
Published: May 2016

In recent years, with the successful drilling of Sha37 and Sha 40 wells and discovery of Yingdong No.1 oil field, great breakthrough had been achieved in Shizigou-Yingdong area. And hydrocarbon exploration in Shizigou-Yindong tectonic belt is also blooming. However, contrast with the great achievement in exploration, research on hydrocarbon accumulation process is still weak and exploraiton potential is not clear. In this paper, several advanced methods are adopted to research the hydrocarbon process including QGF and QGF-E analysis on core sample, TSF analysis on oil sample and laser confocal scanning on component analysis of hydrocarbon inclusion. The results of analysis on hydrocarbon inclusion and oil sample by new methods showed that there were mainly two stages (N21 and N23-Q) of hydrocarbon accumulation in this area. Early hydrocarbon charging is mainly low maturity oil and latest charging is high maturity oil and gas. Meanwhile, new concept and dynamic model of structure evolution in western Qaidam baisn demonstrated that the inverse "S" shape structure were formed controlled by Alyn Tagh and East Kunlun strike slip fault. Structure of Shizigou-Yingdong area were first formed in the west and developed eastward. Hydrocarbon accumulation are mainly controlled by regional fault and preservation conditions. The footwall of fault and the eastern part of Yingdong tectonic belt are favorable for hydrocarbon accmulation. The new understanding on hydrocarbon accumulation process and favorable enrichment prediction has great significance to the further exploration and well deployments.

Introduction

Shizigou-Yingdong area located in the western Qaidam basin, where several oil fields including Gasikule, Youshashan, Shizigou and Wunan had been discovered before 2000(Fig.1). There were not big oil or gas fields discovered in the last decade until Yingdong oil field was discovered in the year of 2010. Yingdong oil field is not only one of the biggest discoveries of CNPC, but also one of the richest oil fields in China. In order to research the hydrocarbon accumulation process and exploration potential in this area, large amount of core and oil samples of Yingdong area and adjacent oil fields were collected and analyzed in our laboratory. After observation and datailed analysis of oil/gas inclusion in reservoir core sample, conventional geochemistry analysis of oil samples, dynamic analysis of tectonic movement, formation and evolution of Shizigou-Yingdong tectonic belt, the two stages of hydrocarbon charging history and accumulation process is identified.
Responsible Unconventional Gas Operating Principles in Practice, Sichuan, China
Authors: Cortis Anthony , Zheng Gary , Castle Martin , Jianghong Wang , Feizhou Guo , Westley Karen
Published: May 2016

Shell has published a set of five aspirational global onshore tight sand/shale oil and gas operating principles that provide a framework for protecting water, air, wildlife and the communities in which we operate. We design our activities using state-of-the-art technology and innovative approaches that make the most sense for local conditions. This paper outlines Shell's implementation of these principles in the assessment and development of a Basin Centred Gas play in partnership with PetroChina in a block in Sichuan Basin, China. The 4,106 km2 block lies in the heart of the Sichuan basin, sometimes referred to as the "bread-basket" of China. The area is intensively farmed and is characterized by very hilly topography with problematic access. Population densities are 500–600 people per km2. The partners are executing a 3-year, 21-well appraisal program designed to evaluate the gas potential and commerciality of the block. A successful Development stemming from this appraisal would allow for an extended production period under the auspices of a PSC. Hundreds, if not thousands of wells, could ultimately be drilled. Operating presents unique challenges from a surface perspective because of the potential impact of our operations on local communities. In accordance with the onshore operating principles, Shell China has developed and implemented a number of operating methodologies that ensure we operate our wells and facilities safely, minimize the footprint of our operations, ensure water and air quality and properly engage with local communities. These methodologies, challenges, success factors and future plans to expand them and further mitigate impacts are discussed in detail.