bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wellbore Stability in Unconventional Shale - The Design of a Nano-particle Fluid
Authors: Riley Meghan , Stamatakis Emanuel , Young Steve , Price Hoelsher Katerine , De Stefano Guido , Ji Lou , Guo Quan , Friedheim Jim 
Published: March 2012

Abstract
Shale-gas plays and other unconventional resources have gained significant importance worldwide. Historically, synthetic-base drilling fluids (SBM) are used in these plays when no environmental concerns are in place and are preferred when wellbore stability is necessary. In this paper, we study the use of an improved water-base drilling fluid (WBM) that is simple in formulation and maintenance that shows excellent rheological properties, maintains wellbore stability, and a good environmental profile. A combination of well-known and economically affordable materials is combined with new technology to achieve desired rheological properties and wellbore stability.
The use of nanoparticles to decrease shale permeability by physically plugging nanoscale pores holds the potential to remove a major hurdle in confidently applying water-base drilling fluids in shale formations, adding a new advantage to the studied fluid. Silica nanomaterials were investigated for this purpose. Due to their commercial availability, these materials can be engineered to meet the specifications of the formation. Characterization of the nanoparticles was completed with Transmission Electron Microscopy (TEM), dynamic light scattering, and X-ray photoelectron spectroscopy. Rheological properties and fluid loss are studied together with other important properties such as shale stability and anti-accretion properties. The authors will describe new laboratory methods used to investigate these properties, from a modified API fluid loss test to the Shale Membrane Test that measures both fluid loss and plugging effects and illustrate additional future research that includes adding reactive species, and anchoring them to the pores, thus stabilizing the shale further.
A Parallel GA-EDA Hybrid Algorithm for History-Matching
Authors: Abdollahzadeh Asaad , Reynolds Alan , Cristie Mike , Corne David 
Published: March 2012

Abstract
To make prudent decisions regarding the exploitation and management of hydrocarbon reservoirs, we need to carry out history matching, a process for conditioning the reservoir simulation model to observation data collected over time. History matching is an inverse problem which requires an optimisation technique to match the simulation results to the measurements. Many techniques have been applied to address this optimisation problem effectively and in efficient time since reservoir simulation runs are computationally expensive.
Genetic algorithms (GAs) and Estimation of Distribution Algorithms (EDAs) are two popular types of evolutionary algorithms. In GAs, new candidate solutions are obtained by applying crossover and mutation operators to a population of feasible solutions according to the principle of ‘survival of the fittest’ in natural evolution. The Estimation of Distribution Algorithm (EDA) is a modern class of EA in which new candidate solutions are generating by sampling from a probability distribution inferred from the better members of the population.
A suitable hybrid of the GA and EDA algorithms can combine beneficial characteristics from each of GA and EDA, while addressing each other’s sources of inefficiency. The main difference between these two EAs is the way they generate new individuals, which results in different exploration/exploitation properties. GAs may sample bad representatives of good search regions and good representatives of bad regions, while the EDA may suffer from fitting a single probability distribution to diverse and distinct regions of good solutions. The hybrid algorithm performs a cooperative search that improves the exploitation and the exploration power of both algorithms.
In this paper, we applied GA, EDA, and a new hybrid GA-EDA algorithm to optimisation of three cases, a test function, the IC-Fault synthetic reservoir model, and one real reservoir, Teal South. The results show that each of these algorithms can be used for exploring the parameter search space in history matching problem. Depending on the problem type, GA, EDA, and Hybrid GA-EDA can achieve good quality matches while they perform a global seach in the space.
Pore Pressure Prediction Using Seismic Velocities for Deepwater High Temperature- High Pressure Well in Offshore Krishna Godavari Basin, India
Authors: Chatterjee Avirup , Mondal Samit , Basu Pramit , Patel B. K. 
Published: March 2012

Abstract
Velocities derived from the seismic data provide indirect estimation of the formation pressure prior to drilling. The uncertainties in velocity estimation increase with the geological complexity and depth which in turn amplify the margin of error in the pore pressure prediction. Such uncertainties can be reduced by adopting suitable velocity to carry out predrill pore pressure prediction. Several advanced techniques for velocity analysis have been used in this study with varying degree of confidence for pore pressure estimation in a deep water HTHP well. The well was designed to drill to a depth of 5000 m with an overpressured Cretaceous clastic sediment column of 2000 m before reaching the reservoir (water depth 600m, maximum prognosed pressure ~11,000 psi and temperature ~190°C).
In deepwater Krishna Godavari basin, the conventional seismic velocity (Handpicked and stacking velocities) based pore pressure prediction resulted in considerable uncertainties in the older Cretaceous sediments as seen in the earlier drilled wells. This called for an advanced velocity analysis (AVO based and Inversion velocities) to reduce the margin of uncertainties for this study well. Such analysis added values to our understanding of the impedance contrast, temporal and spatial variations of velocity in terms of reservoir and non reservoir inter-relationship. A definitive predrill pore pressure curve, taking into account these geological and geophysical factors was the best estimate for well planning. HTHP well drilling challenges can be constrained by depth of top of overpressure, narrow pore-frac window and large ESD-ECD variations due to high temperature gradient. The definitive pore pressure curve catered to limiting all the three critical parameters as comparison with the post drill pore pressure analysis showed a variation of ±0.5ppg. Future deepwater HTHP prospects can be planned by the similar work flow as the drilling experience of this prospect was satisfactory.
Experimental Study of Sea Line Pigging in Unsteady State Two-Phase Flow
Authors: Davoudi M. , Khorrami Z. , Khoramdel I. 
Published: March 2012

Abstract
The main objective of this study is to thoroughly investigate and comparing empirical and simulation results for two-phase flow during the pigging in hilly-terrain pipelines to calculate the amount of slug versus pig velocity. The high slug volume was received in slug catcher after pigging operation of sea lines related to phases 4 and 5 gas plant located in south pars gas field, south of Iran, caused liquid carry over to down stream units and total plant shut down. Beside of liquid level in slug catcher, some parameters such as liquid bottle level, and slug catcher pressure were measured during pigging time process. The results showed that during pigging process, the liquid slug volume was increased from 2100 (m3) to 4100 (m3) by decreasing the gas flow rate from 700 (ton/hr) down to 400 (ton/hr) during pigging operation. The experimental data were compared with the results of mathematical modeling of process by using SPS dynamic simulation software. The relative errors between experimental data and mathematical modeling of the process were 23.8% and 9.1% for gas flow rates of 700 (ton/hr) and 400 (ton/hr), respectively.
Dynamic Simulation for Optimising Pigging Frequency for Dewaxing
Authors: Bansal Rajeev , Ravishankar B , Sharma S S , Afzal Kamran 
Published: March 2012

Abstract
The presence of paraffin in crude oil often leads to wax deposition in pipelines when temperatures reach below Wax appearance temperatures. It is possible to simulate the wax build up using thermodynamic and kinetic/deposition models for estimating wax deposition with varied degree of accuracy. The most popular remediation technique for wax removal is direct mechanical cleaning using pigs as these are generally cheaper than chemical inhibitors. The pigging frequency is mostly determined using thumb rules and operating experience. Correct pigging frequency is essential to avoid significant wax build-up in pipeline that may lead to plugging or stuck pig. This becomes more acute in subsea lines where insufficient well head pressures driving the pig may not scrap out the wax plug ahead of pig. This can increase to downtime and can lead to expensive pipeline repair.
In Mumbai offshore pigging is most common method of wax removal in well fluid lines. In this paper a simulation model using dynamic simulator for predicting daily wax build-up and pigging shall be discussed. The model is based on the actual pipeline condition, fluid parameters and pigging data. Extensive lab studies on actual comingled well fluid samples from platform have been carried out for capturing the Fluid & Wax properties.
The model has been used to run what if scenarios by varying the pigging frequency for the pipelines. The impact of ambient temperature or increase in gas (lift gas) in well fluid on pigging has been studied. Sensitivity studies have been carried out for various parameters like wax plug friction, bypass opening, change in well fluid parameters, etc.
HPHT Gas Well Cementing Complications and its Effect on Casing Collapse Resistance
Authors: Yuan Zhaoguang , Schubert Jerome , Teodoriu Catalin , Gardoni Paolo 
Published: March 2012

Abstract
The failure probability of casing collapse is high in HPHT gas wells because of the cementing complications and the operational environment. In the life of a well, the cement sheath not only provides zonal isolation but also supports casing and increases casing collapse resistance. Due to the high temperature high pressure conditions, the cement sheath plays a more important role in maintaining wellbore integrity. During the production process in HPHT gas wells, the pressure differential inside the casing and the surrounding formation is larger than the conventional wells, this presents a greater challenge to the casing integrity.
Casing eccentricity, cement voids and cement channels usually are cementing complications in HPHT gas wells. Pore-pressure was also considered in this study. In the analysis, the finite element method was used and 2D simulation model was built to study the effect of cementing complications on casing collapse resistance. In the study, two cement systems, brittle cement system and elastic cement system, were used to analyze the effect of the cement property on the casing collapse resistance. In the sensitivity analysis, void location, void size and shape, casing eccentricity, pore pressure, casing internal pressure, horizontal stress, cement Young’s Modulus, cement Poisson ratio, hole diameter, and formation temperature were considered to study their effect on casing collapse resistance.
The results showed that an improvement of collapse resistance of 12% is observed in various conditions in elastic cement system. Casing collapse resistance is very sensitive to void location, cement Poisson’s Ratio, cement Young’s Modulus, and pore-pressure. Casing eccentricity and voids shape have minor effect on the casing collapse resistance. Simultaneous cement channeling and casing eccentricity is the worst case scenario in casing collapse resistance.
This study gives a better understanding of casing collapse failure in HPHT gas wells and helps improve cement and casing design to maintain wellbore integrity that can be expected to last for the life of the well.
Application of Self-Diverting Acid System for Stimulation of Multilayered Wells in Carbonate Reservoir: A Case Study
Authors: Sarma Dilip Kumar , Rao Y R , Mandal B , Bhargava P K 
Published: March 2012

Abstract
During acidization of multilayered wells, major portion of the acids preferably enter into high permeable layers bypassing the low permeable layers. To combat the challenge a self-diverting acid (SDA) was developed with conventional chemicals for effective stimulation of all the layers. The technique involves a stable retarded acid system, a plain acid, a viscous diversion system and a chemical formulation for taking care of wettability issue of the formation rock. Descaling and formation preconditioning were also included for effective treatment and flow back. Two polymers were evaluated in the laboratory for customization of diversion system. The concentration of polymer was optimized to achieve the optimum viscosity required to divert the acid based on the reservoir properties and the flow back after the treatment.
The technique has been implemented in 31 multilayered wells of Mumbai High, a major offshore oil field in India, consists of multilayered carbonate reservoirs, with substantial heterogeneities among the layers. All the candidates were selected with MDT approach. Well specific treatment designs were carried out considering the damage mechanism, reservoir properties and well completions. The treatments were designed in multiple stages of preflush, acids, diversion systems and postflush. The chemical formulation for wettability alteration was used in selected wells.
The placement was carried out by bull-heading and real time treatment plots were recorded in each job. The treatment plots indicate effective acid exposure and uniform stimulation among the layers. Post treatment analysis indicated significant oil gain. This paper will cover the critical areas of stimulation in multilayered wells, details of the SDA technique, treatment methodology, design and post treatment evaluation.
Continuous Improvement in Drilling with Rotary Steerable System in Mumbai High Field
Authors: Soni S. C , Bhargava Ajay , Desai Amit B , Kumar Rakesh , Suryadi Hendrik 
Published: March 2012

Abstract
Application of Rotary Steerable System(RSS) drilling in one of the biggest Indian offshore field, Mumbai High was driven by the increasing difficulties associated with directional drilling by mud motor technology, especially in Extended Reach wells. ONGC has focused largely on finding economic and competitive ways of exploiting the mature and depleted field. Rotary Steerable System provides the opportunity to reach farthest unexploited subsurface targets without adding new platforms with significant improvement in drilling performance and challenging subsurface objectives.
Since first application in the year 2004, RSS has successfully overcome the drilling challenges & problems, especially in 12¼"section, deliver improvement in drilling time. The paper will discuss in detail, each step of continuous improvement in RSS applications & operations, field specific bit design, drill string, fluid system modifications and real time drilling optimization during the last seven years. The actual result on overall directional drilling efficiency enhancement after implementation of each optimization methodology is also discussed.
The discussion covers some unique RSS applications in Mumbai High Fields such as:, drilling top hole 17-1/2" section to complete the well in required hole size, drilling 8-1/2" multilateral section including open hole sidetrack, drilling 6" with RSS & pro-active geo-steering technologies keeping the well in good reservoir with high penetration rate and long horizontal drift. Based on the field results and performance analysis it is concluded that continuous up gradation of mud system, bit design, string design and real time monitoring with proven technology of RSS lead to successful completion of high drift wells.
Fracture Assisted Sandstone Acidizing, Alternative Approach To Increase Production in Tight Sandstone Reservoir
Authors: Gunawan Haris , Susanto Hermawan , Widyantoro Barkah , Noguera Jose 
Published: March 2012

Abstract
The proven and most suitable stimulation technology to increase production in a tight sandstone formation is hydraulic fracturing. The hydraulic fracturing treatment will create a fracture and then keep it open by proppant, hence a conductive path allowing more oil and gas to be produced. Hydraulic fracturing operations in an offshore environment are sometimes considered as a costly solution and non-economic. An alternative economic solution, Fracture Assisted Sandstone Acidizing (FASSA), was evaluated. Sandstone acidizing is a method to increase oil production, by injection of compatible acid system at matrix rate, below the formation fracture gradient. This stimulation method is most suitable to remove near wellbore damage in medium-high formation permeability. To improve the effectiveness of the acid treatment in tight sandstone reservoir, a hydraulic fracture was created prior to the sandstone acidizing. Besides removing the near wellbore damage, the acid is expected to react with fracture face in sandstone and create a conductive path for oil to flow. Four successful jobs have been performed to date. This paper will describe planning, process, acid treatment selection, operation summary, and evaluation of success or failure of the treatment. In the future we also propose to perform similar treatments for a tight reservoir without having to pull out the existing completion.
Decision Making in Upstream Oil and Gas Industry - An Integrated Approach
Authors: Deore Prakash 
Published: March 2012

Abstract
The research presented in this paper is based on existing decision theory and literature used in the oil and gas industry. The outcomes of the study would provides an evidence that in oil and gas industry there is a strong linkage between the use of integrated decision making approach, informed decisions and hence good process performance. The existing state of decision making in industry is being limited, in terms of both user and its functionality per se.
Also it is commonly acknowledged that organizations have not really used as it was predicted at its conception. Allthough, there are initiatives under smart oilfield programs, where organizations are considering integrated approaches of decision making, and that would be the way forward to optimize process time, efforts and cost.
The bottleneck for lower attention to integrated approach is that there is no study or experience captured on improved performance metrics or parameters. Some of the recent surveys indicated from different industries, that making use of integrated approach, efficient tools and standard methodologies in decision making process can help individuals and organizations to meet their objectives.
Initial part of this study introduces decision making and its standard process flow componants. Subsequent part of the study elaborates existing state of decision making in the industry, and integrated decision making approach to new investment analysis in upstream. Lastly, it ascertains the importance of process, method, tool selection for making an informed decision and further optimization.
Well Placement Optimization in a Mature Carbonate Waterflood using Streamline-based Quality Maps
Authors: Taware Satyajit , Park Han-Young , Datta-Gupta Akhil , Bhattacharya Shyamal , Tomar A. K. , Kumar M. , Rao H. S. 
Published: March 2012

Abstract
The placement of infill producers and injectors is an important aspect in the overall development strategy of any field and is particularly challenging for mature fields with high levels of water-cut. Previous screening approaches based upon static reservoir quality maps have limited applicability as these do not account for the drainage and swept volumes from existing wells. In contrast, direct application of formal optimization methods such as evolutionary algorithms and adjoint-based methods to high resolution geologic models may better represent reservoir dynamics but can be complex to implement or computationally prohibitive.
We propose a novel method for well placement optimization that relies on streamlines which represents the flow paths in the reservoir and the time of flight which represents the travel time of fluids along streamlines. Specifically, the streamline time of flight from the injectors provides swept volumes for injectors whereas streamline time of flight from producers gives drainage volumes for producers. These quantities can be effectively combined to a ‘total time of flight’ to locate the potential regions of unswept and undrained oil in the reservoir. Our approach utilizes a dynamic measure based on the total streamline time of flight combined with static parameters to identify potential locations for infill drilling. Areas having high value of the dynamic measure (sweet spots) are both poorly drained and poorly swept, making them attractive for drilling infill wells.
We show the power and utility of our proposed method on a mature offshore carbonate field in western India. The simulation model was history matched using a hierarchical history matching approach that follows a sequence of calibrations from global to local parameters in coarsened and fine scales. Using our proposed method on the history matched model we obtained a dynamic measure map highlighting areas suitable for drilling infill wells. Finally, we compared the performance of infill wells located using the dynamic measure map with wells located using traditional well placement techniques, for example, oil saturation map from simulation. Our proposed method consistently outperforms the traditional approaches. Subsequent field infill drilling in the field has validated our approach.