bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Discrete Element Method for Realistic Modeling of Reservoir Rock
Authors: Nabipour A. , Sarmadivaleh M. , Asadi M. S. , Sabogal Polania J. M. , Evans B. , Rasouli V.
Published: February 2011

One of the most important concerns in perforation operation is to reduce the extent and severity of damage caused by perforating the reservoir formation in order to maximise production. In contrast to several experimental studies on modeling perforation, not many numerical attempts have been made for modeling this process.

In this study a Discrete Element Method (DEM) based code was used for perforation modeling. After generating the rock sample using an assembly of bonded particles, the advantages and shortcomings of the method are discussed. By pointing out the differences between real perforation conditions and modeling assumptions, a number of practical solutions for improvement of the numerical model are explained. The simulated rock sample is then perforated and model behavior was analysed. The results show that the porosity around the peroration tunnel initially decreases due to rock compaction. This is followed by an increase in porosity due to stress release. Results are in accordance with experimental studies reported by other researchers. Stress monitoring around the perforation tunnel provided the ability to analyse the stress shock generated during the perforation process.
The Fracturing of Deep Non-Conventional Volcanic Reservoir - A Case History Raageshwari Gas Field, Onshore India
Authors: Vermani Sanjeev , Gupta Anish , Spitzer Winston , Stolyarov Sergey , Arora Gaurav , Dean Greg
Published: February 2011

Raageshwari gas field is a relatively deep (3000m) non-conventional volcanic reservoir with a gas column in excess of 800 meters. Gas from Raageshwari field is used to generate energy for production of waxy high pour point crude of the nearby Mangala, Bhagyam and Aishwariya Fields (which were discovered in January 2004) in Barmer Basin, Western Rajasthan India (Figure 1, 2). Extensive laboratory studies have been conducted prior the hydraulic fracturing treatments to evaluate rock mechanical properties, rock -frac fluid interaction and mineralogy. MiniFrac analysis was performed prior to the main frac treatment in order to have a better understanding of the reservoir properties prior to pumping of the main hydraulic fracturing treatment. Microseismic fracture mapping was used to determine fracture geometry and azimuth. Fracture modeling was also used to determine effective fracture geometry which was later calibrated to the Microseismic data. Different techniques have been successfully utilized to overcome extreme fracture complexity and resultant screen-outs including proppant slugs, 100 mesh and high viscosity slugs.
Reservoir Management with Real-Time and Periodic Surveillance Data
Authors: Kabir C. S. , Ismadi D. , Fountain S.
Published: February 2011

This paper demonstrates the value of collecting and interpreting real-time data. With an intensive data gathering strategy, starting at wells’ inception to the mature production phase, we show how transient pressure and rate data can be used to manage a complex carbonate gas reservoir. In particular, reservoir connectivity is discerned with pulse testing and with the leading-edge p/q graph, and continuous updates of in-place volume are made with both static and dynamic material-balance methods and corroborating the same with rate-transient analysis.

Interwell connectivity information was deduced during underbalanced drilling by way of interference test between two pairs of wells. Thereafter, transient-pressure tests on individual wells characterized the layered, dual-porosity system, with production logs corroborating the notion of layering. Production maturity over three years has paved the way for estimating connected in-place gas volume associated with each well using the transient-PI, and also with a new method introduced here. This new approach entails plotting both static and dynamic material-balance data on the same graph, yielding the same solution.

Errors associated with real-time rate measurements presented interpretation challenges for rate-transient analysis; however, application of a physics-based filtering algorithm resolved this issue. Flow-after-flow tests that were embedded in monthly variable-rate production allocations, in turn, allowed us to obtain average-reservoir pressure explicitly to do the static material-balance analysis.
Incorporating Motivation and Inspiration Into Learning
Authors: Michael Smith , Edwards J. T. , Woo George
Published: February 2011

Many companies have career advancement training programs. As an employee gains knowledge and improves skill expertise, there is opportunity for that employee to grow within the company.

As trainers, we set a minimum passing score or requirement for the student to gain certification. Students often see the minimum score as what they need to achieve; sometimes students will ask the day before a final exam, "what is the minimum grade I need on the final exam to pass the course?" That minimum score then becomes the goal of the student. As trainers we would like to see the best from the student, not the minimum.

Whether this attitude comes from a lack of confidence or from a lack of effort, the results are the same. How much assurance can we have in a workforce that just meets the minimum requirements? We need to motivate each and every student to do their best. Enhancing the knowledge and skill expertise of the student will improve their overall job performance.

This paper focuses on motivating, inspiring, and encouraging students to strive for their best. Recently several personal award programs were implemented which provide instant student recognition for outstanding work or achievements. Excellence is rewarded not only in the class, but also acknowledged at the workplace. Because of this improvements have been seen in individual efforts. Furthermore, increases in percentage of students passing courses have been documented. The results with case histories are detailed in this paper.
Enhanced Reservoir Scenarios Management Workflow
Authors: García Alejandro , Rebeschini Jordani , Martins Diego , Vieira Carlos , Nunes Fabiano , Da Silva Edilon , Herdeiro Marco
Published: February 2011

Historically, oilfield development has been technically and economically challenging, primarily as a result of more complex reservoirs and difficult environments. One of the roles of a reservoir engineer who encounters these challenges is to provide fast and accurate scenario analyses for management to use for making decisions. During a reservoir scenario analysis process, data management tasks required to get all results in context for successful analysis are always a challenge for engineers to respond in a fast and accurate way, besides the numerical simulation time that is already highly time consuming.

This paper presents a workflow and an environment, developed and implemented for an offshore asset in Brazil, to support reservoir and planning engineers in the generation and analyses of operational scenarios and their management. The goals of this workflow include reducing time-consuming tasks with an automated process, and to facilitate and accelerate the flow of information among key decision makers.

The scope of this work includes case study requests, updating key files in the process, running simulations, processing results, and supporting historical scenarios management. It also incorporates an alternative for conventional numerical simulation with the use of proxy models that aid in the search for an optimum scenario of production and injection profiles.

The effect of the work is primarily focused on the support provided to the engineers to reduce the time required for data management tasks and to locate requested solutions more quickly. The time reductions are highly visible, especially in data management tasks, but they are significantly more important in optimization workflows, reducing the number of regular simulations required to determine the best operational profiles.
Accurate Estimates of in-situ Porosity and Permeability Data Using Cloned Parametric Stressed Models—A Hybrid Approach
Authors: Williams Steve O. , Batarseh Samih , Solanki Max
Published: February 2011

A major drawback in the optimal use of historical core data in reservoir description and exploitation is that most of the core porosity and permeability data are measured at ambient or near ambient conditions of 200 or 400 psi. The use of ambient core porosity and permeability data in reservoir evaluation without appropriate correction to reservoir conditions will result to some degree of uncertainty in reserves determination and flow performance predictions.

This paper presents a methodology for accurate estimation of in-situ porosity and permeability data by first using the flow unitization approach to capture reservoir heterogeneity and delineate the reservoir rock samples. Furthermore, it uses the error minimization technique to clone the non-linear and double exponential relationship of porosity and permeability versus stress, thereby unraveling cloned parameters that are used in the stress model development.

This sound numerical approach was developed and validated using core porosity and permeability data from the Ventura Avenue field, California, where porosity and permeability values are low and variable and reservoir sand quality mix is non-homogenous. Predictions using these models show a correlation coefficient of 0.90 for porosity and 0.85 for permeability, boosting the use of these models in both homogenous and non-homogenous reservoirs. Other existing methodologies in the industry are examined and compared with this robust approach and the results are promising and show a more improved and accurate prediction stress models.
Incorporating Motivation and Inspiration Into Learning
Authors: Smith Michael , Edwards J. T. , Woo George
Published: February 2011

Many companies have career advancement training programs. As an employee gains knowledge and improves skill expertise, there is opportunity for that employee to grow within the company.

As trainers, we set a minimum passing score or requirement for the student to gain certification. Students often see the minimum score as what they need to achieve; sometimes students will ask the day before a final exam, "what is the minimum grade I need on the final exam to pass the course?" That minimum score then becomes the goal of the student. As trainers we would like to see the best from the student, not the minimum.

Whether this attitude comes from a lack of confidence or from a lack of effort, the results are the same. How much assurance can we have in a workforce that just meets the minimum requirements? We need to motivate each and every student to do their best. Enhancing the knowledge and skill expertise of the student will improve their overall job performance.

This paper focuses on motivating, inspiring, and encouraging students to strive for their best. Recently several personal award programs were implemented which provide instant student recognition for outstanding work or achievements. Excellence is rewarded not only in the class, but also acknowledged at the workplace. Because of this improvements have been seen in individual efforts. Furthermore, increases in percentage of students passing courses have been documented. The results with case histories are detailed in this paper.
Design and Application of a New Acid-Alkali-Surfactant Flooding Formulation for Malaysian Reservoirs
Authors: Elraies Khaled A. , Tan Isa M.
Published: February 2011

A new Acid-Alkali-Polymeric Surfactant (AAPS) flooding formulation has been developed to overcome the precipitation problems caused by the divalent metal cations prevalent with conventional ASP flooding. The acid was evaluated in an acid- alkali-surfactant formulation using sodium carbonate and introducing a new polymeric surfactant derived from Jatropha oil. The effect of the new formula on IFT, viscosity, and oil recovery was studied using natural seawater having a large quantity of divalent metal cations. The tolerance of the AAPS towards natural untreated sea water was monitored for 90 days at 90 °C. No precipitations were formed with the acid additive, while precipitations were always generated without the acid. A combination of the new system was found to significantly reduce the IFT between Angsi crude oil and AAPS solution. The most outstanding feature of the AAPS formulation lies in its viscosity insensivity towards an increasing alkali concentration up to 1.2%. Core flood tests with alkali and acid concentrations of 0.6% and 1% respectively confirmed an optimum surfactant concentration of 0.6%. Using the optimum AAPS concentrations, another series of core flood were conducted by changing the injection volume. Only a small incremental recovery was obtained with AAPS slugs higher than 0.5 PV. Injection of 0.5 PV of the formulated AAPS slug followed by chase water produced an additional 18.8% OOIP over water flooding. The benefit of the new system is the use of seawater rather than softened water while maintaining the desired slug properties.
Multiphysics of Coal-Gas Interactions: The Scientific Foundation for CBM Production and CO2 Storage in Coal
Authors: Liu Jishan , Chen Zhongwei , Qu Hongyan
Published: February 2011

Coal permeability is perhaps the most important parameter for the implementation of primary methane recovery and CO2-ECBM technology. It is well known that sorption-induced strain and thermal gradients have significant influence on permeability change. In this study, a general form of permeability model is developed, which includes the impact from the geomechanical process, coal swelling/shrinkage, gas pressure change, and thermal change. Then it is extended to apply on three different coal mediums: (1) Unfractured coal; (2) Fractured porous coal media; (3) Fractured coal with rigid matrixes. Based on this permeability model, a set of governing equations is built up, which fully couples the geomechanical deformation, gas and heat flow processes. This coupled model is used to evaluate the influence from different media types on permeability evaluation, gas injection and production performance, and the effective stress change around the wellbore. In addition, numerical simulations under both isothermal and non-isothermal conditions are conducted. Significant influence on the permeability evolution, injection and production performance was observed for both cases.
Key Factors Sensitivity Analysis on Blowout Probability in Dangerous Drilling Conditions Applying Different Technical Solutions
Authors: Masi S. , Molaschi C. , Zausa Z. , Rossi N. , Michelez J.
Published: February 2011

Blowout is one of the most significant threats associated with exploration and exploitation of petroleum resources, with the potential to cause injury as well as environmental and economic damage.

This paper will present the approach for complex probability evaluation and discuss a sensitivity analysis of blowout occurrence factors for two challenging situations: High Pressure wells drilled using the Closed Hole Circulation Drilling (CHCD) technique and High Pressure / High Temperature (HP/HT) wells drilled using a conventional technique. As such, a risk assessment approach is recommended to properly face blowout probability. In the first scenario (where the primary barrier to well influx is jeopardised), the analysis will predict the level of safety risk and identify any additional procedures and/or additional equipment that may be required. In the second scenario, the analysis will identify the proper safety procedures and equipment required for challenging drilling conditions.

The complex probability evaluation uses fault tree analysis. This allows the consideration of the real condition of the operations including equipment, operating resources and environmental conditions, all broken down to their smallest subsystem (basic event). Each basic event failure rate is then determined using statistical databases.

However, anywhere new technologies, equipment and procedures are implemented, and thus are not yet represented in historical statistics, the reliability of a standard fault tree analysis could be degraded. Therefore, where historical statistics is limited, it is possible to add variability in the fault tree, ultimately combined through a stochastic simulation, to reduce the uncertainty in the fault tree analysis.

By comparing the two challenging conditions using a probabilistic fault tree, this paper shows that the key factors affecting the considered drilling scenario can be different, such that further investigation in the form of a blowout causes/events analysis may be necessary. These key factors are not only technical, but also organizational and human.

Recommendations for preparatory works to minimise the likelihood of a blowout will also be presented.
Dual Casing Running for Deep Water Spud In
Authors: Molaschi C. , Sormani E. , Dallera S. , Fraser T.
Published: February 2011

Nowadays the traditional techniques applied to set Conductor Pipe and surface casing are not able to ensure sub sea well head stick up and verticality and their application depends on soil characteristics to cross.

eni-deep water dual casing (e-dwdc®) has been introduced to overcome these problems. It provides to drill one "tapered hole" of two different diameters in one unique drilling phase, using a tandem BHA, then run in tandem C.P. and surface casing with the inner string and cement in a unique operation. To perform this job, any modification of the equipment is necessary and it is always feasible. If water depth is lesser than the length of surface casing or technical rig constrains exist, dual casing can be however applied but less time saving is possible.

This technique is now considered to be mature for its standard implementation: nowadays 10 riserless phases have been performed, using different rigs and facing challenging environment situations.

Compared to the initial purpose, the field applications demonstrated that several other advantages can be obtained: hole aging is minimized, a time saving is possible if flat time is exploited, the latch between LPWH and HPWH is performed at surface. This technical paper will analyze in detail planning, development and also the ongoing improvement of the system, to allow a contingency remedial job.
Valuation of Swing Contracts by Least-Squares Monte Carlo Simulation
Authors: Willigers B. J. , Begg S. H. , Bratvold R. B.
Published: February 2011

Natural gas and electricity are commonly traded through swing contracts that enable the buyer to exploit changes in market price or market demand by varying the quantity they receive from the producer (seller). The producer is assured of selling a minimum quantity at a fixed price, but must be able to meet the variable demand from the buyer. The flexibility of such contracts enables both parties to mitigate the risks and exploit the opportunities that arise from uncertainty in production, demand, price, etc. But how valuable are they? Traditional Net Present Value, based on expected values, cannot value this flexibility, and the traditional options-valuation techniques could not model the complexity of the terms of such contracts.

Taking gas contracts as an example, this paper seeks to (a) raise awareness of how flexibility creates value for both parties and (b) show how Least-Squares Monte Carlo Simulation can be used to quantify its value in dollar terms, from the perspective of both producer and buyer. Since the value of flexibility arises from the ability it gives to respond to fluctuations (such as in commodity prices), a useful model of swing contracts needs to reflect the nature of these fluctuations.
New Method for Predicting the Average Pore Diameter Using the NMR Data Calibrated to Core Analysis in a Clastic Reservoir
Authors: Reda Ahmed , Hashem Abdel Hakim , Darwish Mohamed , Nashaat Mohamed
Published: February 2011

The Nuclear Magnetic Resonance (NMR) logging is one of the most efficient technologies in reservoir evaluation and characterization due to its wide range of applications. The efficiency of this technology comes from the mineralogical independent acquisition that is only measuring and reflecting the formation fluids but not the rock matrix. This advantage differentiates NMR measurements from conventional wireline electric logging where their measurements, which are affected by the rock matrix and fluid-filled pores and are more sensitive to the rock matrix than to the pore fluids.

Such NMR applications are porosity, permeability, saturations, fluids identification as well as pore size distributions reflecting the corresponding grain size of the rock. The NMR T2 bins distribution reflect the pore sizes distribution of the rock in the presence of only a single fluid in the pores i.e. 100% water saturated rock of water wet nature. In a short inter echo spacing experiment is used, the surface relaxation becomes dominant and then the NMR T2 decay becomes directly proportional to pore size. By assuming the similarity of shape geometries, the largest pores should have the highest T2 values and lowest S/V ratio, and as the pores become smaller, the T2 values become lower and the S/V ratio increases. Therefore, the average pore diameter can be predicted from the measured NMR T2 values, S/N ratio and the rock relaxivity.

The paper explores an efficient and accurate method for determining the average pore size of rock using the NMR data of both the Halliburton-MRIL and Schlumberger-CMR tools calibrated to core analysis. The method is based on identifying the pore shape using the thin sections core chips and using the shape geometry in mathematical approach for determining the average pore diameter based on the reservoir relaxivity and the NMR decay time logarithmic mean. This paper will also detail the application of this method in three different reservoirs, where two are gas-bearing, located in the deep water of the Mediterranean Sea and the third light oil-bearing reservoir located in the Nile Delta depositions.
Well Integrity Assessment and Assurance: The Operational Approach for Three CO2 Storage Fields in Italy
Authors: D’Alesio P. , Poloni R. , Valente P. , Magarini P. A.
Published: February 2011

In 2004 Eni E&P launched the "GHG (GreenHouse Gases) Project" to develop technologies and select fields suitable for geological sequestration of CO2.

For the well area, such project has implied:

Well Integrity Assessment - Verify and (if necessary) reinstate the structural integrity of the existing wells. Well Integrity Assurance - Establish the technical requirements to ensure the integrity of new CO2 injection wells.

Well Integrity Assessment has been carried out by developing and implementing an operational methodology for three Italian fields: Cortemaggiore, PACS (Palino-Ascoli-Candela-Satriano) and Giaurone-Armatella-Gela. Such methodology includes the comparison between the Sustained Casing Pressures (SCP's) measured in the annuli and the relevant Maximum Allowable Pressures (MAP's) to estimate how much each well is close to lose its safety conditions. Then, the methodology foresees specific investigations for the critical wells to identify the magnitude and possible causes of the SCP's occurrence. Finally, it includes the preparation of suitable remedial and/or monitoring plans.

Stress Analysis studies supported the above activities by calculating the mechanical resistance, under the planned operational conditions, of production casings and tubings of the CO2 injection wells.

As far as Well Integrity Assurance, technical requirements for new CO2 injection wells have been established based on the project for the well Cortemaggiore 157 Dir, constructed to carry out the pilot test for the injection of CO2 in a depleted level of the Cortemaggiore field.

Specific studies have been carried out for the PACS and Giaurone-Armatella-Gela fields. The former is a gas field with high CO2 content: CO2 will be separated and re-injected; the latter is an oil field: CO2 injection will be used as an effective means for enhancing oil recovery.

This paper describes the operational approach followed for the above mentioned activities and the main requirements for the new CO2 injection well.
Evaluating Hydraulic Fracture Geometry from Sonic Anisotropy and Radioactive Tracer Logs
Authors: Scott Michael P , Johnson Raymond L , Datey Ashish , Vandenborn Craig , Woodroof Robert A
Published: February 2011

In developing a new field or reservoir, many parameters are important in understanding the success or possible areas for improvement in hydraulic fracturing. Estimating fracture geometry is essential to effectively calibrate a reservoir model to production results. Radioactive (RA) tracers have been used in hydraulic fracturing treatments to infer fracture dimensions. Three stable isotopes (i.e. Scandium, Iridium and Antimony) were used in various parts of the treatment to understand the progression of hydraulic fracture growth. Advanced sonic anisotropy logging tools, using a broader range of frequency acquisition, were used to enable shear measurement in cased hole environments over a wide range of interbedded coal, shale and sandstone sequences both before and after the hydraulic fracture treatment. Amplitude and anisotropy changes after a hydraulic fracture have been measured using sonic anisotropy logging and used to infer fracture height. Finally, the sonic anisotropy can be evaluated above and below the perforated interval and investigate hydraulic fracture height growth away from the wellbore, potentially visualising a greater distance than available with RA tracers. We will show how sonic anisotropy and radioactive tracer logging methods can be used to better understand the fracture geometry and aid further design work.

The paper will present data from two (2) wells in the Walloon Coal Measures of the Surat Basin where both RA tracers and sonic anisotropy logs were used to infer fracture dimensions. Both wells used a combination of treated water stages, containing low concentrations of proppant, followed by borate-crosslinked gelled water stages with higher concentrations of proppant. This project contained a large amount of other hydraulic fracturing diagnostics including treatment pressure history- matching, microseismic monitoring and surface tiltmeters. In this paper we will note how those diagnostics compared with the results presented herein, but their results are discussed in greater detail elsewhere (Johnson et al. 2010a). Generally, the results indicate good agreement between these two fracture diagnostic methods and the authors will illustrate the complimentary nature of these diagnostics in gaining a fuller understanding of fracture height, especially in environments of complex fracture development.
Utilizing Current Technologies to Understand Permeability, Stress Azimuths and Magnitudes and their Impact on Hydraulic Fracturing Success in a Coal Seam Gas Reservoir
Authors: Johnson Raymond L , Glassborow Brent , Scott Michael P , Pallikathekathil Zachariah John , Datey Ashish , Meyer Jeremy
Published: February 2011

In coal seam gas (CSG), also known as coalbed methane (CBM), appraisal, the development potential of a play requires an understanding of the interrelationship between stress and permeability, critical elements in defining deliverability and hydraulic fracturing effectiveness. Unfortunately, the interdependency of these variables may not emerge until the post-treatment evaluation of a hydraulic fracturing treatment. Herein is an example from the Walloon Subgroup (WSG), Surat Basin, where regional data were used to target a small, localized, structural setting for CSG appraisal and subsequent hydraulic fracturing.

Due to the rank of the WSG coals in this area, the cleat network was deemed to be immature and permeability is understood to be derived from exogenetic fracturing from external stresses acting on the coal, creating a unidirectional fracture network. The fractures are commonly constrained to brittle lithologies and truncate at bedding boundaries, while evidences exist of minor low angle faulting in non-reservoir lithologies. Eventually, the local stress regime was determined from the petrophysical log data, injection stress testing, and subsequent one-dimensional (1D) mechanical earth model (MEM). Ultimately, these data support the proposed reservoir and stress environment.

We will show how data were acquired, evaluated and integrated to support the development of the 1D MEM and aided the interpretation of the hydraulic fracture treatment results. While localized, the results of this evaluation indicate a potential pitfall can exist in some CSG environments. This case illustrates a scenario where stress and dominant permeability axes can be properly aligned to maximize hydraulic fracture effectiveness, but where sub-optimal stress magnitudes prevent achieving the full benefit of the hydraulic fracturing process.
Quantum Effects Imparted by Radio Frequencies as a Stimulation Method of Oil Production: Part–II
Authors: Mike Brown J. , Becker Harold L. , Darby Greg
Published: February 2011

This paper is a continuation of SPE 124144 where a new method of stimulating producing wells using electromagnetic frequencies was described. This technology uses tuned energy waves to alter molecular bonds in the well tubular and near wellbore areas which stimulates production increases by disrupting damaging deposits and altering relative permeability in the near-wellbore area.

Additional studies have been completed to further elucidate the mechanism of action and range of application. Many field applications have been completed and some results are presented here. Case studies discussed encompass producing wells in New Mexico, Oklahoma and Texas. Pre and post-treatment production history have been analyzed and the results presented.

Variations in treatment applications were investigated; antenna deployment and configuration, power level and duration, frequency combinations and duration between treatments.
Recovery Mechanisms and Oil Recovery From a Tight, Fractured Basement Reservoir, Yemen
Authors: Legrand Nicolas , de Kok Joop , Neff Pascale , Clemens Torsten
Published: February 2011

The fractured basement field in Yemen described in this paper is characterised by two types of fracturing: background fractures with a very low effective permeability of less than 0.001 mD and fracture corridors with an effective permeability of up to 1 mD. Except for some dissolution porosity related to fracture corridors, no significant matrix porosity is encountered (total porosity is 1.15 % only). About half of the oil in place is contained in the fracture corridors and half in the background fractures.

Production from this field commenced in 2006. It is currently produced by depletion. Compositional grading has been observed in the 3120 ft oil column. Despite the fact that the oil is at bubblepoint pressure at the top of the reservoir, a moderate increase in gas/oil ratio (GOR) has been seen.

Detailed simulation studies revealed that the reason for the slow increase in GOR is the low permeability of the background fractures. The low permeability leads to viscous forces being dominant over gravity forces and hence almost no gravity segregation of gas and oil.

Due to the relatively small viscosity difference of the gas and the oil in this field, the gas mobility is not much higher than the oil mobility at low gas saturations. Hence, oil and gas are produced effectively from the background fractures into the fracture corridors and the reservoir pressure is not depleting as fast as in reservoirs with higher viscosity difference of gas and oil.

A number of reservoir management strategies have been investigated. The results indicate that the low permeability of the fracture corridors and very low permeability of the background fractures results in challenging conditions for increasing oil recovery by water or gas injection. However, the efficiency of depletion drive is higher than in conventional reservoirs.
An Innovative Approach to Heat Heavy Oil Formations by Means of Two Horizontally Interconnected Wells
Authors: Poloni R. , Sassi G. , Valente P. , di Campli A. , Bianchella D.
Published: February 2011

In the last years, several technologies have been developed to either allow or increase production from heavy oil fields. The greatest challenge is to reduce oil viscosity by heating in depth the formation. Despite the availability of many methods, there is no one that is at the same time technically efficient, economically profitable, environmentally-friendly and applicable to all types of heavy oil reservoirs. This still generates a large amount of research investments for the Major Oil Companies.

Eni E&P has initiated an R&D project based on the innovative concept of interconnecting two horizontal wells. The main objective is to realize a closed circuit to allow the continuous circulation of a superheated fluid across a lengthy horizontal section. The heat transferred from the fluid to the formation will reduce viscosity of the heavy oil inside the reservoir and will improve its recovery. The fluid to be circulated will be "super heated" by means of thermodynamic solar energy.

All the above make the method studied by Eni E&P applicable to almost all types of heavy oil deposits, characterized by a high technical-economical efficiency and highly eco-friendly. Several aspects are involved in the achievement of such a closed circuit and need to be considered while performing drilling, intersecting and tubing running operations.

Specially fit for purpose well profiles and casing/open hole schemes are foreseen in order to correctly reach the reservoir with the intended hole section and align the two wells with a suitable "bridge" (casing or liner). Due to the very high temperature involved in this application, in the above mentioned R&D project there is consideration in developing new materials and welded casing pipes.

This paper will describe the approach, the status of the project and the expected results.
Formation / Well-Bore Current Conditions Integrated Characterization by the Full Wave Acoustics to Conduct Fracturing
Authors: Dobrynin Valery M. , Gorodnov Andrey V. , Chernoglazov Valery N.
Published: February 2011

The selection of well candidates, planning and evaluation of hydro fracturing (HF) efficiency are based on the information from well log data. The technology of full wave acoustics logging, developed at Russian Gubkin State Oil&Gas university under the professor V. M. Dobrynin supervision [1] enables for single log run obtain the integrated information regardless the current formation properties, perforation interval and casing cement bond.

The acoustic technology is based on analyses of kinematics and dynamics parameters of main informative waves of acoustic field – compress ional, shear and Stonley waves. The data processing and interpretation are conducted by Kamerton computer system. The algorithmic basement of interpretation is modified Bio-Gassman model of differential elastic media.

The acoustic technology of HF information assistance consists of two acoustics logs – before and after HF. From the first log, before HF, following data are obtained: the current formation oil saturation, total and dynamic formation porosities, permeability, elastic-deformation rock properties, the power of hydrodynamic formation/well connectivity at perforation interval, cement bond quality. The second acoustic log is conducted after HF implementation. Based on the second run data the interval of rocks properties changes (due to HF) are determined, sections of rocks compaction and destruction are obtained, he changes in hydrodynamic formation/well connectivity are evaluated, the changes in cement bond conditions are estimated, the interval and azimuth of sub vertical HF fracture are estimated.

The practice of acoustic technology implementation `confirms there comprehension for different well conditions, for variable rock properties, and applicability for different types of acoustic devices-from the most simple three element zonde to the modern cross dipole zonde.

The rock properties changes due to HF implementation are favorable to study by acoustic.

The acoustic technology enables provide integrated characterization of current well and formation condition witch are necessary to check the effectiveness of HF.
Critical Oil Rate and Well Productivity in Cold Production From Heavy-Oil Reservoirs
Authors: Guo Boyun , Ai Chi , Qu Jianfang
Published: February 2011

Cold heavy-oil production with sand (CHOPS) has been widely used for recovering heavy oil from unconsolidated sandstones (UCSS). Although this technology is considered to be mature in some oil fields in Canada, there are some technical issues that need to be addressed when this technology is transferred to the fields in other parts of the world. This is mainly due to the variations in local geological and reservoir conditions. One of the concerns is whether the designed well production rate is high enough to self-clean the wellbore against sand accumulation. During planning of CHOPS completions, it is imperative to know if the designed fluid production rate will be adequate to carry sand to surface, especially when horizontal wells are employed, where significant amount of sand can accumulate in the horizontal wellbore that can kill the well. However, it is not clear as what constitutes the "adequate" fluid production rate. A theoretical investigation of sand transport in heavy oil was conducted in this study. A critical fluid production rate was defined to quantitatively describe the "adequate" production rate required to carry sand to surface in vertical, inclined and horizontal wells. Also developed in this study is a CHOPS-well deliverability model based on self-stimulation of reservoir and oil-water-gas-solid 4-phase flow in the production string. Combined use of the critical production rate model and the well deliverability model allows for optimal selection of pumps that will ensure the smooth production of fluids in CHOPTS operations. This paper provides petroleum engineers essential knowledge and information for planning CHOPS well completions.
Characterization and Modelling of Asphaltene Precipitation and Deposition in a Compositional Reservoir
Authors: Figuera L. , Marin M. , Lopez L. , Marin E. , Gammiero A. , Granado C.
Published: February 2011

This paper presents results of phase behavior calculations and simulation of asphaltene precipitation and deposition in The Carito-Mulata Field, based on a reliable experimental support. The Carito-Mulata Field is a complex compositional system which changes from gas condensate at the top to an under saturated black oil in the flank. In this area Asphaltene precipitation becomes a serious problem where plugging of the formation, wellbore and production facilities dramatically affect the productivity and final recovery of the area. To help to prevent the asphaltene precipitation a high pressure maintenance project has been applied by gas and water injection. Therefore it has been considered mandatory to define a representative numerical model to predict the phase behavior of asphaltene precipitation and deposition.

As first part of this study a complete experimental plan was carried out involving several PVT analyses, measurements of precipitation onset pressures and plugging core analyses. PVT analysis was used to match a Peng-Robinson EOS in order to reproduce the phase behavior of the system. Asphaltene precipitation as function of pressure was modeled by a pure solid model which was matched by measurements of precipitation onset pressures. A Solid deposition model was matched based on core analysis to reproduce the reduction of porosity and permeability by asphaltene deposition.

At the end, a simulation study based on a radial single-well and a 3D model was carried out to validate the predicting model and analyze the Impact of the asphaltene deposition in the well productivity and how it affects the efficiency of different production strategies. It was compared to the impact in the design of production plans taking into consideration the asphaltene modelling and not taking this into consideration. Also it showed how the reported observations in the field, in Lab and in the literature were adequately reproduced.
Enhancing Water-flooding Effectiveness of the Heavy Oil Reservoirs by Using the Viscosity Reducer
Authors: Zhang Fusheng , Ouyang Jian , Wu Muxi , Wang Guijiang
Published: February 2011

On the basis of analysis of components and structure of the heavy oil from the 109-1 block in the Dagang oilfield, the high effectiveness viscosity reducer, which can make the mixture of water and heavy oil to become the stable O/W emulsion and decrease viscosity of the heavy oil by above 97% in the case of above 30% water cut and above 1000mg/L dosage of viscosity reducer (for total amount of water and heavy oil), have been developed according to the characteristic of high temperature 80, high mineral salt 20693.75mg/L (especially Ca2+/Mg2+ 805.38 mg/L) and the lower recovery percent of reserves of the 109-1 block heavy oil reservoir in the Dagang oilfield. The viscosity reducer in the produced liquid did not bring unfavorable influence on demulsification. The core displacement experiments show that displacement system containing viscosity reducer can enhance oil recovery by above 22% comparing to water-flooding, and prove that decreasing heavy oil viscosity can improve the oil-water mobility ratio, enhance sweep efficiency and enhance oil recovery.
ICD Design: Revisiting Objectives and Techniques
Authors: Daneshy A. Ali , Guo Boyun , Krasnov Vitaly A. , Zimin Sergey V.
Published: February 2011

Inflow Control Devices (ICD) were developed in response to early water break-through from the heel of prolific horizontal wells. In their initial applications, the design of ICD installations was based on equalizing flux (flow rate per unit length) along the length of a horizontal well, which required "choking" of flux in the heel region. In practice, these tools are often installed along the entire length of a horizontal well, with the logic that since choking level is proportional to flow, the tool will automatically produce a more uniform flow profile.

In this paper we will re-examine the technical validity of attempting to achieve equal flux along the length of the horizontal well. We will show that in reservoirs with uniform permeability the flux from the toe and heel regions should in fact be larger than the mid-section. We will also show that delaying water or gas breakthrough is not a sufficient reason for use of ICDs. We will discuss the benefits of a new design philosophy whereby each well segment is choked at a level that regulates its flux to a level that produces an outcome more suitable for optimum reservoir management. This gives the operator the flexibility to design ICD layout to optimize various flow parameters, including time or cumulative production at water/gas breakthrough, location of first water/gas breakthrough, etc. This will be especially valuable for wells in variable permeability reservoirs. A new design simulator developed based on above concept will be presented and its benefits demonstrated through a case history.
How good is the P90 Value as a measure of the Reserves Downside?
Authors: Gupta Sandeep , Gupta Ritu , van Elk Jan , Vijayan K
Published: February 2011

Probabilistic methods for reserves estimation, including uncertainty quantification and probabilistic aggregation, have gained widespread recognition in the oil and gas industry, since the first comprehensive guidelines were issued by the SPE in 2001. The probabilistic methods now used, as proposed in these guidelines, are similar to those also used in portfolio theory by the finance industry. A lot can be learned from the extensive experience with probabilistic methods and quantification of risk with measures like Value-at-Risk in portfolio theory. Especially, the guidelines issued by the Basel II Accord and since the recent financial crisis contain important lessons.

As a first step, we examine a fundamental question. Is the P90 reserves value an appropriate measure for quantifying the reserves downside? For the P90 value to be considered a good measure of the reserves downside, it needs to possess a number of basic characteristics involving P90 for each field and the probabilistically aggregated P90 value for the portfolio of fields. We define these characteristics and through examples will demonstrate that the P90 reserves estimate, in general, meets the requirements of a good measure of reserves downside. A possible uncertainty scenario, where some of these characteristics do not hold, is also given. An alternative measure of risk, specified as the average reserves over the confidence interval higher than P90, for quantifying reserves downside is presented.

In this paper, we will highlight the appropriateness and limits of using the P90 reserves estimate as a measure of the reserves downside. Understanding of the limitations posed by using the P90 value is vital in management of reserves risk.
Quality Check of Gas-Condensate Pvt Studies and Eos Modelling under Input Data Uncertainty
Authors: Schebetov A. , Rimoldi A. , Piana M.
Published: February 2011

Reservoir simulation is the key tool to design a field development plan and to evaluate field production performances. Various software products have been created and Oil&Gas industry has gained a broad experience of their application. Creation of the reservoir fluid PVT model (PVT table for reservoir simulators) is an essential part of any integrated reservoir studies. PVT models are usually generated using mathematical algorithms by means of equations of state (EOS).

Whenever fluid PVT models are created for the reservoir simulation a variety of uncertainties in the input data arises due to deficiencies of laboratory equipment, low accuracy and quality of sampling techniques, especially for gas-condensate fields. This paper presents a unique know-how in quality control of PVT studies and application of advanced modeling methods using the EOS.

After identification of main uncertainty sources, a quality check procedure was developed to assess the consistency of PVT samples and to select the most reliable ones for EOS modeling. This procedure is based on simple criteria and should be used to handle with uncertainties in PVT studies.

A generalized EOS tuning algorithm was designed and hereby presented in a form of step by step flowchart which summarizes authors’ experience in EOS modeling. Additionally a new method to modify a reservoir gas composition for a proper initialization of the reservoir simulation model as well as for removing possible inconsistencies in the input data is proposed.

The workflow suggested by the authors was successfully implemented in several reservoir simulation models of the gas-condensate assets managed by LLC SeverEnergia, in West Siberia.