bluuebunny/crossref_metadata_2025_split huggingface dataset:
Holistic Life Cycle Costing Approach for Different Development Phases of Drilling Tools
Authors: Johannknecht F. , Gatzen M. M. , Hahn D. , Lachmayer R. 
Published: November 2016

Abstract
Considering the current trend oil and gas corporations are facing, they are continuously focusing on increasing their operational efficiency. Declining oil and gas prices lead their operational departments to reduce the cost of drilling and producing hydrocarbons, which ultimately results in streamlining the operational cost of their drilling tools. Oilfield service companies with hybrid business models must take all life cycle cost into account. To influence these costs and to optimize capital and operational efficiency as well as service availability, comprehensive cost models are used in the product development process. For the consecutive development stages from feasibility through detailed design, models with increasing level of detail are required.
Cost modeling within the development process is typical in the petroleum industry. Currently, models are available for specific applications in single development phases. This paper describes a holistic approach to analyze and optimize life cycle cost and service availabilities of drilling systems from the early concept phase through deployment. The result is a fast, secure and easy usable software tool as well as a standardized process to develop competitive, high-technology drilling systems.
To identify requirements for these models, a stakeholder analysis is performed and described. Based on the analysis results, information flows are defined: Who provides and needs which information at what point of time within the process? With this foundation, new models are created or existing models extended to meet the requirements. In this context, best practices from different industries are also reviewed and implemented where applicable. A parallel use of the models during the respective development stage enables an iterative improvement. The development of the models and current results are detailed in this paper.
In early conceptual design phases, it is challenging to calculate life cycle cost with sparse information about the complex future drilling system, so cost-estimating relationships must be devised. Maintenance times and intervals, which are one of the main operational cost triggers, must be assessed by concurrent high level tool performance and reliability. Cost efficiency, tool performance and reliability must be balanced to achieve high customer expectations and high margins. During the detailed design phase, system costs, such as alternative costs, e.g., through non-availability of tools, in addition to bottom-up models on the component level, must be considered. These modular models are connected to each other to exchange data via standard interfaces. They calculate future cost projections and identify key cost drivers. This enables continuous cost optimization through the whole development process. Results to support decision-making as well as cost saving potentials are shown with an exemplary development process of a drilling tool by using the life cycle costing approach.
A Simulation Model of Land-Facies Karamay Oil Sand Reservoirs Under Water Injection
Authors: Pang H. , Jin Y. , Chen M. , Lin B. , Shan Q. , Xu Z. 
Published: November 2016

AbstractThe micro-scale hydraulic fracturing is a technique which is used to shorten the preheating period by means of controlling water injection to horizontal wells to create homogenously distributed microcracks in the zone between the two wells. Numerous simulation studies have been previously conducted to understand the growth of the steam chamber, however, the model to simulate mini-frac before preheating is left undone. Especially, counterpart research on land facies ultra-heavy oil sand of Xinjiang oilfield is few.The provides micro-scale hydraulic fracturing model, in this study, is based on experimental analysis in terms of geomechanics theory and mini-frac tests result from field experiment in Xinjiang oilfield. First, laboratory triaxial tests were designed to determinate the mechanical behavior of the oil sand and the mudstone caprock. Drucker-Prager model was used to investigate the two dilation mechanisms, namely, shear dilation and tensile parting, during the simulation of micro-fracturing propagation. Finally, a micro-fracturing model coupled fluid-solid is implemented by with the finite element program ABAQUS, to describe the early SAGD start-up demonstrated on the SAGD well pair in Xinjiang oilfield.The first-hand target of ABAQUS simulation in this study is to evaluate the performance of micro-fracturing process, particularly, to determine the degree of connectivity of injection and production wells. Thereby to predetermine the bottom hole pressure (BHP) and volume of injection in order to provide a specific guidance for work program carried out in oilfield. As the matter of convenience, this study, according to the simulation results, have discussed how to define the extent of the connected parameters to determine the connectivity of the well pairs. Furthermore, sensitivity analyses have been done to realize the different parameters on proficiency of micro-scale hydraulic fracturing in the field.Our works are significantly important for the future development and promote the mini-frac tests to enhance the in-situ thermal recovery in Xinjiang oil field. In addition, the model and method can be implemented for any type of heavy oil field which requires early SAGD start-up to increase the oil recovery.
Smart, Porous Polymer Coatings to Bind Clay Minerals in Coal Bed Methane Wells
Authors: Ge Lei , Hamilton Christopher , Ferbina Tasha Rahman , Rudolph Victor , Rufford Thomas E. 
Published: November 2016

Abstract
We report a phase inversion polymer coating to prevent clay swelling and fines production in coal seam gas (coal bed methane) or other petroleum well bores. Importantly, this coating remains permeable to gas and water flow across producing coal seams. This approach uses a water-soluble solvent that can form a low-porosity, dense membrane across clay-containing interburden layers, which contain less free water than the coal matrix, but form a porous membrane across the coal layer. Problematic interburden samples and reference coal samples were from a core sample obtained from a coal seam gas well in the Surat Basin, Queensland. The mixture of polymer coating solution (polyethersulfone (PES)/N-methyl-2-pyrrolidinone (NMP)) was prepared and cast onto the target samples by a simple dip method, followed by the phase-inversion step. Polymer coatings were characterised by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The SEM images of coated mudstone and coated coal samples showed that the polymer formed a dense layer across the low-permeability mudstone, but an open porous structure was formed on the coal surface. The uncoated rock samples and polymer coated samples were exposed to a flow of distilled water, and the formation of any fine particles was observed by video camera. The flow tests show that the PES coating can significantly improve the stability of interburden samples containing swellable clays.
The Mechanism of Complex Hydraulic Fracture Creation Due to Strength Heterogeneity
Authors: Nagaso M. , Mikada H. , Takekawa J. 
Published: November 2016

AbstractUnderstanding the mechanism of complex hydraulic fracture creation could develop a design and management of subsurface fluid paths in hydraulic fracturing. Although many studies about fracture network formation caused by various geophysical factors has been conducted, the influence of strength heterogeneities of rock is not fully revealed. We perform a series of numerical simulations of hydraulic fracturing with a particle method to reveal the generation mechanisms of hydraulic fractures whose geometrical complexity could depend on strength heterogeneities of subsurface materials. We use microscopic strength distribution, which is set randomly to follow the Weibull distribution, in our models as a substitute for the strength heterogeneities of real subsurface material after confirming the validity of this substitution by numerical analysis of uniaxial tensile tests. As a result of numerical simulations of hydraulic fracturing with our models with a range of strength heterogeneities, we found geometrically complex fractures are comparatively generated in the models as the increase in the strength heterogeneities. Because of weak interparticle connections included in the model due to heterogeneities, micro cracks are generated to cause the furcation of advancing hydraulic fractures around their tips. The further propagation of hydraulic fracture is strongly affected by these preceding micro cracks, and hydraulic fracture does not propagate straightly and complex network of hydraulic fractures is created. In addition, pores with specific shape and microscopically weak portions cause fracture to be complex. The direction of tensile stress induced by fluid infiltration depends on the shape of pores and fractures. The tensile stress would act in the maximum principle stress direction at the pore with specific shape and newly fracture perpendicularly to main hydraulic fracture is formed from the portion of weak strength at the pore wall. On the other hand, the models with weak strength heterogeneities show a simple linear extention of hydraulic fractures because fewer branches are formed around the tip of the advancing hydraulic fractures. In conclusion, micro cracks generated around the tip of hydraulic fractures and pores with specific shape cause the hydraulic fracture to become complex geometrically in the model after the furication with strong microscopic strength heterogeneities.
Success in Arresting Overall Field Decline and Increasing Oil Production in a Mature Field through Effective Production Enhancement Initiatives
Authors: Zamanuri A. , Abdulhadi M. , Chin H. V. , Lim C. C , Jacobs S. , Sayed Zainaiabidin S. M. A. , Khalil M. I. M. , Abd Wahid M. I. , Dolah K. A. , Munandai H. 
Published: November 2016

Abstract
In a mature oil field that has been producing for over 30 years, declining reservoir pressure and increasing water-cut are the two major factors that are affecting oil production rates. It is a common understanding that without any effort, this decline in oil production will remain until the end of the field's economic life. One of the approach to address this issue is through production enhancement work which has been proven successful in an oilfield offshore of Sarawak not only at arresting the overall field decline, but also increasing the overall oil production.
The practice for Production Enhancement (PE) work in this field mainly involves (i) shutting off the existing watered-out intervals, (ii) adding perforations to the existing sand and/or a different reservoir, (iii) zone change and gas lift valve change activities, (iv) re-activation of idle wells, (v) gas lift optimisation and well bean-up, (vi) reservoir management planning and (vii) restoring well integrity.
Due to the limited deck space on the platform and the unavailability of living quarters, the application of a work barge was essential for this type of PE work to house the necessary equipment and chemical for the enhancement job as well as acting as an accommodation vessel for the personnel. Concurrent well intervention operations on two different platforms was the selected option for time and cost optimisation and quicker first oil. For the same reasons, 24 hours operation was implemented whenever circumstances permitted. Further cost optimisation was implemented in subsequent campaign by utilizing slickline only as means of well intervention as well as withdrawing the option to have a dedicated work barge on site to support the campaign.
After the successful PE Campaign in four (4) consecutive years, this initiative has resulted in over 3500 bopd of incremental oil. The overall technical potential (TP) of the field also increased by more than 100 percent. This has effectively arrested the previously estimated 25 percent field decline before the campaigns and increased in the overall field production. This paper seeks to present the challenges, the plans and operational execution of the well intervention activities. The results of the successful PE campaign, implementation of best practices, lessons learnt and improvement plan will also be shared.
Geomechanical Models: Application to Drilling in Partially Depleted Fault Blocks
Authors: Rana Rohit , Hansen Kirk S. , Kandpal Jyoti , Kumar Rajan , Schutjens Peter , Muro Leytzher , Rees Daniel , Latief Agus I. 
Published: November 2016

Abstract
Knowledge of the in-situ stress state and how it varies with reservoir depletion is important for the design and execution of in-fill drilling. This paper highlights the key geomechanical aspects and their usage in planning of wells through severely depleted (up to 25 MPa) and overpressured zones within a very short depth interval (few 10s of m), in an onshore gas field in Brunei. With focus shifting from oil to deep-gas development, drilling complications include risks of wellbore instability, excessive mud loss and internal blowouts, as well as differential sticking in the depleted reservoirs. Moreover, fracturing of the depleted sands while drilling infill wells carries the risk of jeopardizing production at nearby producing wells because of locally altered flow paths. The risks were evaluated by application of empirical and analytical geomechanical models of stress changes with depletion, and by elasto-plastic finite element models of borehole instability (collapse) due to shear failure.
Our results show that for an average depletion rate of 1 MPa/year, the drilling window (difference between maximum allowable mud weight controlled by fracture pressure and minimum mud weight controlled by formation pore pressure or borehole collapse pressure, whichever is greater) is likely to remain open for the coming 12 years. Minifrac or extended leak-off tests at different stages of field development should be taken to monitor stress changes within the reservoirs and provide updates for calibration of the geomechanical model.
Next to showing the geomechanical model results and their application to drilling, we demonstrate the refinement of pore pressure/fracture pressure predictions (i.e. narrowing down the uncertainty in the drilling window) for mature fields where producing "from the bottom up" has not been feasible. We also indicate how risks associated with drilling through depleted/undepleted reservoir sequences in a single hole section can be managed to as low as reasonably practicable with the help of geomechanical input. These results "open the door" for accessing deeper potential pay zones by drilling through severely depleted formations.
Optimisation Leads to Improved Hybrid Bit Design and Enhanced Drilling Efficiencies in Challenging Vertical Application in Tarim Basin, China
Authors: Liu Y. , Chen M. , Sheng S. , Zeng J. 
Published: November 2016

Abstract
This paper describes the optimization of a hybrid bit which is a polycrystalline diamond compact (PDC) bit with rolling cone cutters to improve dynamics and durability. When drilling the hard & interbedded formations with conglomerates in the Tarim Basin in Northwest China, PDC bits break down with broken & chipped cutters in the cone, nose & shoulder sections of the profile. In addition severe torsional vibrations lead to twist-off's and stick-slip which damages the bit and drilling system. Even worse, because of the torsional vibration, less Weight on Bit (WOB) is being applied, which results in lower Rate of Penetration (ROP), less footage and more trips. Roller-cone bits generally drill faster than PDC bits, but bearing life is short in the hard and abrasive conglomerates.
Due to success in similar application elsewhere in the world, a hybrid bit was proposed and tried to drill the challenging formations in the Tarim Basin. In the first run the entire conglomerate interval was drilled at higher ROP, with lower torsional oscillations and saving 16 rig days. Although this was a success there was an opportunity for further improvement by strengthening the PDC cutting structure to avoid premature cutter damage mainly in the central, cone section of the profile.
An upgraded hybrid bit with split, overlapping blades and more durable Dual Chamfer cutters was deployed in the same interval. Respective performance of PDC, Roller Cone, Hybrid bit and Optimized Hybrid bit used in the same formation are compared in terms of footage, ROP, Mechanical Specific Efficiency (MSE) and dull condition. By using Optimized Hybrid bit, the customer saved multiple bit runs & drilled eight times farther with the ROP 92% faster than conventional PDC bit run in the same well.
A Two Dimensional Approach to Saturation Computation in Laminated Reservoirs
Authors: Farag S. M. 
Published: November 2016

Abstract
Laminated reservoirs where traditional shaly sand interpretation techniques underestimate the true formation hydrocarbon saturation, are common in South East Asia. Logging technology such as tensor resistivity measurements, nuclear magnetic resonance (NMR) and high resolution log analysis have been shown to be the best way to accurately evaluate such reservoirs; however, these logs can only be recorded in new wells. A simple technique to re-evaluate existing wells and compute more accurate fluid saturations using "conventional" logs (resistivity, density, neutron and gamma ray in this case) is proposed here.
From our experience with tensor resistivity and high resolution analysis, it is a good assumption in many laminated reservoirs that the effective water volume (Vwee) in the individual sand laminations remains roughly constant over short intervals. Traditional shaly sand interpretation is usually performed point by point with no assumptions about the continuity of the results. If we assume that Vwee in the individual sand laminations is roughly constant over a depth interval, then it is possible to invert for Vwee as long as the total shale volume is varying over the interval. We still need to make the usual assumptions about the conductivity of the shale and formation water needed for traditional shaly sand analysis. However, by simultaneously inverting over multiple depth levels, we can derive a narrow range of possible Vwee solutions. In suitable conditions, the resulting total water volume computation is much more accurate than conventional shaly sand analysis in laminated reservoirs.
The proposed interpretation method has been tested in several wells from different areas, to establish the range of applicability and limitations. The results compare favorably with tensor resistivity interpretation where the resistivity contrast between sand and shale laminations is moderate. As the sand to shale resistivity contrast increases, the method becomes more sensitive to the input parameters and the uncertainty increases. In all cases, the computed saturation is more accurate than standard point by point shaly sand interpretation in laminated intervals. Since the inversion outputs a range of solutions rather than a single value, the method has a built-in estimate of the accuracy of the results.
In suitable conditions, this formation evaluation technique extends the usable range of "conventional" log data in laminated shaly sand environments. This is especially useful for re-evaluating producing fields where drilling new wells and acquiring tensor resistivity and high resolution logs in the laminated facies is not practical. Details of the proposed interpretation workflow and quality control of the results are presented.
Three Dimensional Stress Field Estimation Using S-Wave Anisotropy Obtained from Ambient Noise Records of Vertical Seismic Array System
Authors: Kimura T. , Mikada H. , Araki E. 
Published: November 2016

Abstract
In this study, we propose a new approach to estimate depth-dependent stress field in a borehole instead of conventional in-situ measurement methods. Seismic interferometry and Alford rotation methods are used to obtain S-wave anisotropy as a proxy of stress field. Ambient noise records observed by horizontal components of vertical seismic array system installed in a borehole were used as input data. We first calculate virtual cross dipole seismic records by seismic interferometry method applied to the observed continuous ambient noise records. Then we applied the Alford rotation and layer stripping technique to obtain depth-dependent S-wave anisotropy parameters, i.e., the orientation of fast S-wave and the difference between fast and slow S-wave velocities of formations along the vertical axis of a borehole. Obtained results, the orientation of fast S-wave, have very good agreement with directions of principal horizontal stress, which was revealed in the analysis of borehole breakout just after drilling the borehole. We propose that our approach would readily be applied to monitor the stress field around a borehole instead of conventional in-situ measurement methods.
A Success Story for a High-Temperature Foam-Assisted Lift Application in a Mature Field, Gulf of Thailand
Authors: Sompopsart Suwin , Toempromraj Wararit , Nadoon Apiwat , Charoencheep Phongsiri , Sukchum Techasit , Harnboonzong Pithak , Whangkitjamorn Jugkapun , Lerlertpakdee Pongsathorn , Thanasutives Patana , Tivayanonda Vartit , Charoenniwesnukul Kritsada , Thongpian Duangkwan , Kultaveewuti Chatsuda , Wongrattananon Chuayrach , Ketpreechasawat Suampa , Wongpattananukul Kongphop , Pulputtapong Jirayu , Sirimongkolrat Saran , Pongsripian Winit , Phanich-aphichai Krittapas , Wattanasuwankorn Reawat , Thompson Stewart 
Published: November 2016

Abstract
Liquid loading is a common problem in many gas wells in the Gulf of Thailand. At the late stage of well life, reservoir pressure declines, gas production rates decrease, and liquid begins collecting on the wall of the tubing and accumulates at the bottom of the well, eventually killing the well. This paper presents promising results from foam-assisted lift (FAL) field trials to remove liquids, re-establish flow, and increase production in previously idle wells.
The injection of foaming agents can be used to remove liquids through artificial lift. High downhole temperatures in Gulf of Thailand wells requires special foaming agents that can operate at 450°F. Using high-temperature foaming agents in nearly dead wells can extend their life by reducing the production decline rate and preventing premature water loadup. Because foam density is significantly lower than liquid density, hydrostatic pressure is reduced, which assists the flow of fluids from the bottom hole to the surface, resulting in increased gas production rates and reserve recovery rates compared to natural flow.
An operator in the Gulf of Thailand experienced promising results from a field trial using high-temperature FAL with batch treatments in five high-temperature wells in the offshore field. Three wells that were previously not flowing were able to flow to the production system after treatment. One well was able to flow at even higher rates after the FAL treatment compared to prejob rates. Only one well did not respond to the treatment. Understanding the FAL procedure and addressing critical issues before implementing the technology can help enhance mature field production in otherwise idle wells.
Using FAL in mature wells with low or no production can help remove liquid accumulation at the bottom of the well, preventing premature water loadup and returning idle wells to production.