bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Skin for High Deliverability Gas Well Tests
Authors: Elshahawi H. , Gad K.
Published: December 2007

In general, any restriction to flow that causes a distortion of the flow lines from being perfectly normal to the borehole direction would result in positive skin. As a result, the skin factor computed from well testing is a widely used indicator of the overall flow efficiency of a given well. This is theoretically valid, but often, a high positive skin indicated from a well test is assumed synonymous with a large extent of near-wellbore formation damage and is, therefore, frequently used as a criterion to perform stimulation treatment meant to enhance the well productivity. This latter practice is generally not valid since the skin factor computed from a well test is, in reality, a composite variable that is not merely a function of near-wellbore damage. This skin factor is also a function of parameters such as perforation geometry, well deviation, partial completion, and other phase and rate dependent effects. Therefore, the skin computed from a well test must first be broken down into its constituent components in order to determine the "true" near-wellbore skin. Moreover, the skin and permeability values computed from a well test are so intimately related that an error in one directly impacts the other. Typically, additional input data would also need to be integrated in any given permeability-skin model in order to reduce the computational uncertainty. Only after proper modeling, can an appropriate stimulation treatment be selected. This is particularly important for high-deliverability gas wells, for which the formation damage-related skin often makes up only a small portion of the total well test-measured skin.

This paper outlines a methodology that can be used to compute the various skin components as well as representative values of the average formation permeability from a well test. Several examples from gas wells are presented to demonstrate the utility of this methodology.
Production Enhancement in the Belayim Fields: Case Histories
Authors: Elshahawi H. , Siso S. , Samir M. , Safwat M.
Published: December 2007

Inadequate productivity of perforated wells has been a major concern since the introduction of cased completions. Petrobel company, operating in the Belayim fields of Sinai, Egypt, and responding to an unpredictably fast decline in field production, launched an initiative in 1996 to identify the under-performing perforated wells in order to plan remedial actions. Since the vast majority of the wells were under artificial lift, this involved the integration of data from various sources. The study revealed that the majority of wells in the field were in fact suffering from excessive damage. Wells were then categorized based on the value of their completion factors (the ratio of actual to theoretical productivity indices), and the potential sources of damage were identified for each category. This was accomplished using techniques such as nodal analysis and skin modeling.

One of the most successful techniques used to cure the damage was the re-perforation of the damaged wells with deep-penetrating perforating charges. Until the use of this technique, and even with attempted improvements in other operating parameters, field performance had continued to fall short of theoretically predicted results. This paper highlights the origin and development of formation damage in the Belayim fields, and how this damage was attributed to different damage mechanisms using a novel combination of nodal and damage analysis techniques. It also presents some cases of dramatic productivity enhancement due to the use of these techniques and the introduction of deep penetrating perforating.
Six Sigma Tools Applied in Automatic Well Testing-Reducing Response Time to ’No Fluid Detected Wells’
Authors: Sihombing Santun , Purnomo Agus , Brahmantyo Akson
Published: December 2007

The Duri oil Field has 3,000 active wells divided into 9 (nine) areas. To measure the volume of oil and water produced, each well is tested approximately twice a month. When an NFD (no fluid detected) condition occurs during the test, the well is not performing properly and should be checked to see what requires repair.

Cycle time to put the well back to production depends on: response time to NFD wells, number of NFD wells found that day, the type of repair required, and the resources available to make the repair. Without intervention, the NFD wells automatically are put back into retest by the programming logic. Historical data from Area-4 in 1999 shows that wells were off production an average of 405 days/month due to NFD status. With a median production of 34 BOPD / well, 450 BOPD was not being produced. At a crude price of 12.5 US $ / barrel the total lost opportunity cost is 2 MM US $/ year.

Starting in late February 2000, the project team began deployment of Six Sigma tools, with the result that the response time was reduced to only 300 days in March and then farther reduced to 140 days in April and May. The number of individual NFD wells was reduced from a 1999 average of 69 wells to 54 wells in March and 25 wells in April and May. The effort resulted in a production increase which equates to an annualized opportunity gain of 1.0 MM US $/ year. The background, objectives, and results of the Area-4 respond time to NFD wells improvement program are presented in the report.
Some Predictions of Possible Unconventional Hydrocarbons Availability Until 2100
Authors: Kawata Yuko , Fujita Kazuo
Published: December 2007

This paper presents several trial calculations on supply and demand forecast of the unconventional hydrocarbons (UHC) under the control of CO2 emission using the Ultra-Long Term Supply/Demand Balance Model1. We performed five cases of variation on the basis of BAU (bussiness as usual) case. As a result, the substantial production of UHC would begin around the year of 2030, and the production cost should jump up to about 1.5 ~ 2 times of the present conventional gas cost toward 2100. Most of the under-developing countries will be fully developed to increase their energy consumption. Thus, transfer of technologies to under-developing countries shall become important and it may be not enough for reducing CO2 emission to expand natural gas consumption only. Therefore, a combination of various measures, in another words, best-mix formula of primary energy supply is essential. Especially, the promotion of energy conservation and the utilization of renewable energies would be more effective measure for CO2 reduction as well as controlling the UHC production cost.
Deepwater Production with Surface Trees: Trends in Facilities and Risers
Authors: Ronalds B. F. , Lim E. F. H.
Published: December 2007

As oil and gas production has moved into deeper water, and with the common requirement for platform drilling and/or frequent well intervention, new solutions have been developed to support rigid risers and surface trees. The four types of dry completion unit employed to date – jackets, compliant towers, TLPs and spars - are described and compared, along with their advantages and current limits of applicability. A database of deepwater production platforms is included.

Platform optimisation cannot be performed in isolation from riser considerations, as the requirements of the risers are intimately related to the operating characteristics of the production facility. This interrelationship, and resulting trends in both platform concepts and production riser configuration, is explored. A key issue is the tendency for the risers to displace vertically relative to the facility, which becomes very significant for softly-moored hulls in ultra-deepwater. This displacement may be accommodated by modifying the riser shape, make-up and method of support.
Gas Slippage in Two-Phase Flow and the Effect of Temperature
Authors: Li Kewen , Horne Roland N.
Published: December 2007

Gas slippage in single-phase gas flow (Klinkenberg Effect) has been investigated extensively. Few papers, however, have been published on the gas slippage in gas-liquid two-phase flow. The gas relative permeabilities at water saturations close to the residual value have been found to be significantly greater than one in both nitrogen-water and steam-water flow through rocks. These values became less than one after the calculation was calibrated by taking the two-phase gas slip effect into consideration. The gas relative permeabilities have been measured at different mean pore pressures and the values of two-phase gas slip factor have been computed at different water saturations. The effects of temperature on both nitrogen and steam slip factors have also been studied and compared. These data have then been used to conduct a calibration in order to obtain intrinsic gas relative permeabilities that do not vary with the test pressures. It has been found from the present work that neglecting the two-phase gas slip effect may overestimate gas relative permeabilities. It is the intrinsic gas relative permeabilities instead of those measured at low test pressure that should be utilized in numerical simulation or other reservoir engineering calculation.
Deployment and Development of Computer-Based Learning for the Upstream Petroleum Industry
Authors: Sargent B. C. , Bihn G. C. , Ford J. T.
Published: December 2007

A unique training initiative utilizing computer-based material and a learning management system, designed to fill experience gaps of professional staff in the upstream petroleum industry, has been developed. This paper introduces and provides a basis for the initiative, and the benefits of using computer-based learning (CBL) in such an initiative.

The focus of the paper is on deployment and development of CBL material, and in particular: The development of training programs using CBLExisting CBL material and the deployment thereofCurrent/planned CBL development and the future of the program

In view of the worldwide shortage of E&P professionals, existing high-quality E&P computer-based training material and an off-the-shelf learning management system (LMS) are being used to expedite deployment of the program. As the deployment of existing material proceeds, the development of new CBL courses varying in breadth, depth and delivery platform is a key element of the initiative and is already underway. In the future both academic degree programs and professionally certified programs with varying amounts of CBL material will be available.

The potential benefits of training programs utilizing CBL are significant. First, the experience level of professional staff can be improved by on-demand, just-in-time learning. Second, the need for instructor-led training (ILT) can be minimized. Lastly, coupled with traditional on-the-job and ILT, innovative CBL material can cost-effectively accelerate and enhance the learning process.
Implementing Enterprise Architecture - Putting Quality Information in the Hands of Oil and Gas Knowledge Workers
Authors: Cox G. A. , Johnston R. M. , Palermo R. M.
Published: December 2007

In their article "Escaping the IT abyss," Jed Dempsey, et. al., said the following: "There's a sense of despair these days in the boardrooms of companies struggling with IT. They are all too aware that information technology is vital to strategic success. Yet their application portfolios are inflexible and difficult to maintain. Their technology infrastructures are complex and hard to reconcile. And their IT organizations are overburdened, overstretched, and overwhelmed" [1].

In the May 1998 issue of JPT, Lesslar and van den Berg sited that in-house Shell studies suggested that technical professionals spend 60% of their time looking for data [2]. In an Oil & Gas Executive article, Baksi said, "Data-management problems are widespread though out… As a result, cycle times are long and assessing the risk associated with interpreted results can be difficult. Further, operating companies often have limited capability to leverage information, knowledge, or best practices among different asset teams or business units" [3].

Our company was formed from a merger followed by a major acquisition and property exchange. This history caused us to have numerous non-integrated legacy systems and inconsistent information management practices. In 1998 we implemented an enterprise resource planning (ERP) system. Although the EPR system brought greater functionality and some integration, we were still left with hundreds of legacy systems and inconsistent data practices. Information in our ERP was difficult to analyze. Initial feasibility studies indicated that, on average, our workers spent 40% of their time searching for and scrubbing data.

After struggling with this for two years, our company decided to develop an Enterprise Architecture Plan (EAP). This paper describes why EAP was chosen as the approach for improving our information management practices, the IT issues facing industry in general, the business benefits of architected systems, and the current status of our EAP implementation.
Uninterrupted Education: The Vital Role of SPE's Continuing Education in Professional Development
Authors: Fattahi B.
Published: December 2007

Traditional formal education, although still fundamental to preparation of individuals to join the ranks of future professionals, has long become insufficient in supplying the necessary knowledge base for the entire journey through a long professional career. The new work environment requires uninterrupted education. To accomplish this, subscribing to knowledge networks, maintaining good technical understanding, and being continually in touch with advancing technologies are critical to new professionals' success.

Professional development programs such as those organized by SPE are vital in providing the opportunity for our industry professionals to obtain the "Just-In-Time" training they need to keep abreast of the advancing technology. This paper presents a discussion on how SPE strives to accomplish its mission of technology dissemination through the continuing education process.
Integration of Production History and Time-lapse Seismic Data Guided by Seismic Attribute Zonation
Authors: Huang Xuri , Bentley Laurence R. , Laflamme Claude
Published: December 2007

Cluster analysis is used to construct fluid flow zones from seismic attributes. The steps are (1) remove grid points that contain outliers in any seismic attribute; (2) scale each attribute to zero mean and unit variance; (3) use principal component analysis to transform the scaled attributes to uncorrelated principal component attributes; (4) principal component attributes are grouped into categories of similar seismic response using cluster analysis; (5) upscale the seismic grid to the computational grid scale using a weighted voting procedure (morphing); (6) spatially filter cluster assignments to remove small, isolated spots using a weighted voting scheme; (7) assign a seismic zone to spatially connected elements with the same cluster category. After zonation, rock properties such as porosity and permeability are perturbed as a group within each zone instead of node by node in order to match historical production and seismic data. Using a Gulf of Mexico test case, the zoning procedure produced useful computational zones and reduced the time required for history matching.
Development of a New Equation and an Algorithm To Estimate Permeabilities for Clean Formations From Resistivity Logs
Authors: Li Dacun , Engler Tom W.
Published: December 2007

Correlation between porosity and permeability for a certain rock type is a basic procedure used in core-data interpretation. However, the correlation may not always be satisfactory due to pore heterogeneity and pore geometry. In a reservoir, it is very common for rocks to have similar porosities but different permeabilities. Apparent formation factor was defined as true resistivity divided by water resistivity. Curves of apparent formation factor vs. water saturation are used to interpolate permeabilities. Unfortunately, the accuracy is limited at high water saturation because the curves are horizontal in that region.

In this paper, a numerical method is proposed to solve the problem. Based on combining a correlation between formation resistivity factor and permeability proposed by Ogbe and Bassiouni, Archie's equation, and the apparent formation factor definition, a new equation is derived to estimate permeabilities for clean formations from resistivity logs.

An algorithm is developed to carry out the procedures of the estimation and an example is given to illustrate how to use the algorithm. A computer program developed from the algorithm can be incorporated into a reservoir simulator as an improved way to input permeability values.
Orifice Meters for Steam Injector Monitoring - How Accurate are They?
Authors: Castrup Suzanne Griston
Published: December 2007

Monitoring the amount of steam distributed to individual injectors is an important part of steamflood management. For many years, attempts have been made to employ orifice meters at injectors to measure steam quality or rate. However, published orifice meter correlations for two-phase steam vary significantly. Of primary concern is whether or not there is a strong correlation between the pressure drop across the orifice plate and changes in steam quality and/or flow rate. It is also important to understand the impact of two-phase flow regime (e.g., slug flow, annular-mist flow, stratified flow, …) on pressure drop across the orifice plate and how it affects the reliability and accuracy of the orifice meter.

This paper discusses the basic principles of steam flow through orifice meters and presents a straightforward analysis of the reliability and accuracy of orifice meters for measuring steam qualities or rates at injectors. Additionally, the problems encountered when using two orifice meters or orifice meter and critical flow choke in series to simultaneously measure injector steam quality and rate are examined.
A New Method for Evaluating the Performance of a New Modular Drilling Fluid System for a Small Turnkey Rig Using Hamiltonian-Lagrangian Minimum Energy Principles
Authors: Hayatdavoudi A.
Published: December 2007

For those who are familiar with the financial risks, it is very clear that showing a profit is not an easy task for a small turnkey drilling company. In fact, a small mis-step could spell disaster for a small turnkey contractor. This is an undeniable fact. It is also true that both Major Operators and Independents alike are sensitive to drilling bid prices even during times of prosperity and favorable oil and gas prices. Beating down the turnkey prices often, in some quarters, is considered a "good sport." What must a small turnkey contractor do then?

In order to meet the challenge of profitability for a small turnkey operator, the author introduced a simple Modular Drilling Fluid System that solved many costly problems. The Modular Drilling Fluid System, in nearly 70 wells, eliminated the "gumbo" problem and cut the drilling days by 20 to 50 percent. The reduction of drilling days, to the contractor, meant increased bit life by as much as 30 percent, savings in fuel costs by about 30 percent, savings in rig repair cost by about 30 percent, and a host of other savings. In this paper, in his comparative analysis, the author examines the bit records and other pertinent field data from three wells drilled in the same field and discusseses the principles of a modern Modular Drilling Fluid System that allowed a small turnkey contractor to become financially and technically successful. Furthermore, for analyzing the efficiency of the operational parameters such as bit hydraulics, weight on the bit, and rotary speed of the same small turnkey rig that drilled the above-mentioned wells, the author uses the simple yet powerful principles of Minimum Energy. This is done in order to quickly and easily point out where it is possible to save on the expenses of the small turnkey contractor. In this method, although more emphasis has been placed on hydraulic and mechanical energy, or power, all of the expended energies or powers of the rig system can be integrated over time. Applying a modified form of a combination of Lagrangian and Hamiltonian Integral1-7 carries out this process. The operational performance of the turnkey drill rig is said to be efficient when the value of this Integral is at a Minimum in comparison with the performance of the other drill rigs, or zero ideally. This technique enables the contractor to closely monitor his daily operational expenditure of Energy or Power and succeed both technologically and financially.
Propped Fracturing as a Tool for Prevention and Removal of Formation Damage
Authors: Bale Arthur , Larsen Leif , Barton David Tudor , Buchanan Alastair
Published: December 2007

Formation damage caused by either fluid invasion, during the process of drilling through the reservoir, or introduced by various mechanisms while producing the reservoir, represents a dominant obstacle to optimum hydrocarbon production. Different stimulation methods/techniques are applied dependant upon the type of completion and the characteristics or source of the damage. This paper focuses on the role propped fracturing can play in prevention and removal of any type of formation damage.
An Engineered Approach to Matrix Acidizing HTHP Sour Carbonate Reservoirs
Authors: Jones A. T. , Rodenboog C. , Hill D. G. , Akbar Ali Anwar H. , de Boer P.
Published: December 2007

Conventionally, matrix acidising treatments have not been performed in HPHT wells with temperatures much above 150°C, because of the limitations on acid retardation technologies of hydrochloric acid (HCl) and the inhibition of corrosion of these fluids at elevated temperatures.

This paper presents the design and operational experience from a treatment performed on a gas well in a naturally-fractured, tight carbonate under conditions that were beyond the limit of conventional matrix acidizing experience. Stimulation of the well required acid to be placed below fracturing pressures into the natural fracture system beyond the near wellbore region. The reservoir was deep, sour and at high temperature and pressure.

Ensuring success of such an operation requires detailed design, involving extensive laboratory testing of fluid properties and design of placement techniques. Additional procedures and equipment are also required to effectively manage HSE risks and well integrity. This paper presents the critical factors in the design and operations planning stages, highlighting these with the case history for this well.
Acid Penetration in Natural Fracture Networks
Authors: Dong Chengli , Zhu D. , Hill A. D.
Published: December 2007

In this paper, we present a methodology for predicting the propagation of acid along natural fracture networks and the resulting etching of the fracture walls. The natural fracture network is modeled as a system of intersecting fractures that form a main pathway for acid transport and dissolution. The tails of the intersected fractures increase the leakoff from the main pathway and are accounted for in the model. The fracture network acidizing model is supported by comparisons with laboratory experiments and smaller scale simulations that determined the nature of acid channeling at fracture intersections. Model results illustrate the effects of variations in fracture properties on acid propagation. The model predicts deeper acid penetration under matrix conditions than would be possible with only matrix flow.
Evaluation of Filter Cake Flowback in Sand Control Completions
Authors: Tiffin D. , Stevens B. , Park E. , Elliott F. , Gilchrist J.
Published: December 2007

Open hole gravel packing for sand control can offer productivity and cost reduction advantages over cased-hole completions, particularly in thick, high permeability sands. The filter cake formed by the reservoir drilling fluid can be trapped by the gravel, resulting in high drawdown requirements, non-uniform inflow profiles and/or low productivity. Effective clean-up and flow-back of this filter cake is necessary to fully realize productivity advantages of open-hole completions.

A comprehensive series of over 20 laboratory experiments were carried out to better understand filter cake flow-back in sand control completions. Variables investigated included mud weight and type, gravel size, additives like enzymes and acids, gravel size, and screen type. Results from 12 of these experiments are summarized in this paper.

Key findings include:

Tested synthetic oil base muds resulted in filter cakes which were much easier to remove than those formed from tested water-based muds. 40/60 mesh gravel can severely inhibit filter cake removal compared to larger gravel sizes, which still maintain sand control. An expandable screen pressed into the filter cake does not inhibit filter cake flow-back as long as solids are sized correctly, i.e. the drill-in mud is properly conditioned at the rig site.

Experiments were conducted in a standard cell where filter cakes were dynamically deposited and allowed to flow back through gravel and/or screens at scaled flow rates – many with gas. Following each experiment, the entire cell was saturated with epoxy and thin sections were cut across the filter cake and gravel. These visual images dramatically complement return permeability and "lift-off" pressure measurements and help illustrate the mechanics affecting return permeability performance.
Strategies for Sizing Particles in Drilling and Completion Fluids
Authors: Suri Ajay , Sharma Mukul M.
Published: December 2007

To minimize formation damage due to drill-in and completion fluids solids must be sized to satisfy two important criteria: (i) they must be large enough to not invade the rock, and (ii) they must be small enough to form filter cake that effectively filters drill solids and polymers from the filtrate entering the formation. These criteria when used together with the model presented in this paper quantitatively define the particle size that should be used in drill-in fluids for a given formation permeability, overbalance pressure and mud formulation.

A model is presented that estimates the depth and degree of formation damage caused by solids of widely different sizes present in drilling or completion fluids. The depth of damage and permeability loss is calculated after the invasion of the mud and also after flowback. The effect of the particle size distribution in the fluid, particle concentration, overbalance pressure, and permeability of the formation are studied. It is demonstrated that particle invasion and flowback processes are largely dependent on the particle size in the mud and the permeability of the formation. The results of the model are shown to agree well with mud filtration experiments.

To better estimate the particle size distribution in drill-in and completion fluids, different methods for measuring particle sizes were investigated. These results show that the measured particle sizes can vary over two orders of magnitude depending on the technique used and on sample preparation. Based on a comparative analysis of several samples light scattering techniques are recommended for measuring the particle size distribution. Recommendations for sample preparation are also provided.
IMPES Stability: The Stable Step
Authors: Coats K. H.
Published: December 2007

An Impes stability criterion is derived for multidimensional three-phase flow for black oil and compositional models. The grid may be structured or unstructured. Tensor considerations are neglected. The criterion can be used to set the time steps in an Impes formulation or as a switching criterion in an adaptive implicit model.

The criterion extends previous work by accounting for three-phase flow, including capillary, gravity and viscous forces, with all the possible cocurrent and countercurrent flow configurations in a general grid. The criterion derivation uses stability theory, to the limits of its applicability, augmented by numerical experimentation, including extensive one-dimensional tests and numerous field study datasets.
Scaling Up of Laboratory Relative Permeability Curves. An Advantageous Approach Based on Realistic Average Water Saturations
Authors: Crotti M. A. , Cobeñas R. H.
Published: December 2007

Accordingly with Welge formulation, to obtain relative permeability curves at laboratory, all calculations are made on a selected point of the sample. Usually this point is located at the outlet face of the sample, where production rates are directly measured. As a result, relative permeability curves are reported as function of point saturations and not as function of average saturations. Laboratory curves are then adapted to reproduce reservoir behavior, usually through the derivation of pseudo functions. With usual methodologies, this pseudo curves are also expressed as function of point saturations and introduced in numerical simulators. In spite of this procedure, numerical simulators perform their calculations using the average water saturation at every grid block. Although point and average saturations are expected to be the same at infinitely small grid size, this is not the case with coarse areal simulation grids.

In this paper, water-cut as a function of produced oil is analyzed for a linear case. Several cases are developed using relative permeability curves defined as function of point saturations for different grid sizes, and as a function of average water saturation. It is shown that only curves with average values give reliable data.

As a result of this work, an advantageous methodology to transform laboratory measured curves into those consistent with numerical simulation approach is presented. It is also shown that the use of rock relative permeability curves, previously adapted to the particular geometry of the system under study, drastically reduces the number of grid blocks required and overcomes numerical dispersion.
Bitumen and Well Behavior in Loma La Lata Field: Summary and Analysis of New Information
Authors: Maretto H. M. , de Vera H.
Published: December 2007

The results obtained during 1999 s drilling plan in Loma La Lata field, related to the bitumen and the reservoir behavior through new information coming from production logs, NMR, and multipolar acoustic logs, formation tester, open hole completions, core analysis, pre-existent geochemical studies and detailed diagenetic descriptions; allow considering the postulate of bitumen generation related to an early migration from Los Molles Formation like more consistent. This bitumen has a wide and regional distribution and its influence should be contemplated in all the units older than Vaca Muerta Formation.

It is considered convenient logs that register the effective porosity to the correction of the conventional ones by some distribution law. In this sense the density of bitumen seems to be sufficiently high as for not affecting the NMR tools.

The porosity of Sierras Blancas Formation is secondary and generated in a second phase of dissolution, being the permeability controlled by rock type and abundance of pore bodies; acquiring importance again the magnetic resonance whose permeabilities and porosities show adjusted values with the petrophysics measurements.

Some layers of the reservoir could behave as tight gas, and the gas would be flowing to wells for channels of high pemeabilities in the main layer of the field. These variations in the units would be related with an intra-Tordillo unconformity and they demand the fracture of the same ones to accelerate their production.
A Novel Methodology To Reduce Formation Damage in Gravel Packed wells: Case Study, Casabe Field, Colombia
Authors: Zapata Jairo , Ferneynes Heberth
Published: December 2007

During the development of a secondary recovery project by water injection in a Colombian field called Casabe it was observed that the packed production wells presented an abnormal declination on production rates. This was initially attributed to the completion type: slotted liners or screen packed with 10/20 or 20/40 gravel. The packings have an average length of 1,200 ft. The partial recovery of a slotted liner and screen demonstrated that there was an impermeable material that plugging the external phase of the pipe by 90%, not allowing the oil to flow into the wells.

The phenomena in question seriously compromised the volumes of production and the life span of the injection project since plugging in the wells generates loss of productivity and represuring in the field causing premature casing collapse.

This article shows the methodology used by teamwork in charge of defining the cause for the plugging in the wells, designing a treatment that would lessen the problem and establishing an operational technique to selectively stimulate the intervals present in the packed wells.
Project Finance in the Brazilian Petroleum Industry
Authors: Ferreira Virgílio José M. , Gonçalves Armando Celestino
Published: December 2007

In order to cover the financial capability of Public sector in the emergingcountries, new ways of financing of the Public expenditure in infrastructureprojects need to be studied. This is the particular case of the PetroleumIndustry in Brazil.

Perhaps, without private capital, both national or foreign, the BrazilianIndustry will never be able to support itself his own consumption demands.Therefore, the use of Project Finance (PF) modeling to meet an alternative wayto Corporate Finance, will be extensively used to substitute the governmentalrole of Public Investor, who, besides, doesn't have more capability to investintensively in Petroleum Projects.

Some advantages brought throughout Project Finance is separation of theproject risk, by the creation of the SPC (Special Purpose Company), whoseaccount life has independence to the players of the project. Otherwise, thiskind of financial modeling is used in projects that require intensive amountsof capital, like oil and gas projects. So, despite the higher cost of capital, the Project Finance alternative can be extensively used to find out his ownsself-sufficient in the production of oil and gas.
Artificial Neural Networks Applied to the Operation of VGO Hydrotreaters
Authors: Lopez R. , Perez J. R. , Dassori C. G. , Ranson A.
Published: December 2007

This study introduces an accurate, generalized method based on a three-layered perceptron artificial neural network (ANN) trained to estimate the continuous operation of a vacuum gas oil hydrotreater. The ANN models predict the fractional composition of paraffins, naphthenes, and aromatics distribution (mono, di, tri and tetra aromatics) contained in a vacuum gas oil (VGO) mixture. Moreover, ANN models were built to simulate the behavior of several process variables such as product flowrate, average reactor temperature and product quality (sulfur content, API gravity, TBP50, metals content, and refractive index).

VGOs proceeding from commercial hydrotreaters were employed to illustrate the use of ANN models to estimate the VGO composition in a very simple manner with no need for knowledge of the system. The artificial neural net models use API gravity, TBP50 and the refractive index of the desired vacuum gas oil to be studied.

These empirical models were tested on experimental data not used during training showing an average error of 0.5 % in the prediction of VGO paraffins, naphthenes and total aromatics content, which is an outstanding performance compared with traditional correlations proposed in the literature.

The hydrotreater reactor ANN models were compared against process data collected from the CRP-Amuay refinery data acquisition system. The results using the ANN model to estimate the reactor EIT (Equivalent isothermal temperature) indicate an average error of 4 °F. Additionally, the product sulfur content prediction reports an average error equal to 6 wt%.
The Use of Fuzzy Mathematics of Finance: Risk Evaluation in Petroleum Development
Authors: de Salvo Castro Antônio Orestes , Martins Fereira Filho Virgilio José
Published: December 2007

• In general, most capital budgeting problems deals with future and often uncertain data. To cope with this uncertainty, fuzzy sets theory has been applied to traditional deterministic approaches by replacing uncertain data with fuzzy numbers. In this paper the bases of The Fuzzy Mathematics of Finance, to model the uncertainties of data inputs is presented, providing anapproach to risk analysis. The goal is to capture and quantify the qualitative information of the project coordinators using linguistics variables and modelthe uncertain cash flow and discount rates as triangular fuzzy numbers. Anexample of fuzzy cash flows and fuzzy resultant net present value (NPV) is computed from the model. Finally, a fuzzy project selection is performed by applying different dominance rules and a comprehensive numerical example is present.
Integration of 3D Seismic and Production Data in Secondary Recovery Analysis, Puesto Hernandez Field, Neuquén, Argentina
Authors: Montagna Aldo , Yañez Pablo Paez , Groba Cristian , Cerutti Andrés
Published: December 2007

The object of this work was to optimize a waterflood project in a highly complex structural-stratigraphic area. A geophysicist, two waterflood-monitoring engineers and a numerical simulation specialist made up the multidisciplinary team created for the project.

The goal was to explain the low response to water injection in the subject area, i.e. the injection well behavior (variation in the admitted volume, overpressurization, etc.), and the corresponding shortage in production wells.

The information used for this study consisted in 3D seismic data, interpreted well logs, correlation, transient pressure tests, production and injection history, hydraulic connectivity analysis and previous structural interpretations. A radioactive tracer test was also conducted.

Seismic cross-section were developed between wells in order to detect structural and stratigraphic lineaments. Then, a seismic attribute analysis was performed. The reflection strength and the amplitude attribute reflected clearly the thickness loss northward and the deterioration of the petrophysical properties toward the east. The instantaneous phase attribute was used to interpret the structural frame but no significant results were obtained. A reliable correlation between petrophysical information and seismic data was achieved.

After defining the structural – stratigraphic frame, the information above was related to the production and injection history of the area. Some old build up and fall off tests were reviewed in order to confirm the existence of faults and petrophysical changes.

Based on this analysis, some proposals were drawn to improve 1the production and injection behavior of the pattern, namely, horizontal drilling from existing vertical wells, acid treatment, hydraulic fracturing and the drilling of a horizontal well in an unswept area.

The reservoir water saturation distribution was evaluated for each proposal using a numerical simulation model and a cost-effective analysis of the proposals was carried out.
Natural Waterflooding, Campo La Peña
Authors: Luis Rivero Jose , Navia Walter
Published: December 2007

Waterflooding is a secondary recovery method widely used in the oil industry implemented with the purpose of increasing additional oil recovery from oil reservoirs. Traditionally the waterflooding projects are implemented by means of injecting water through water injector wells in order to maintain or improve the reservoir pressure and to sweep the oil towards the producer wells.

The purpose of this work is to present a novel waterflooding alternative called natural waterflooding. This natural waterflooding method attempts to use the water and energy from a higher pressure reservoir to a lower pressure reservoir. The natural waterflooding method will be implemented to La Peña reservoir of La Peña Field throughout a crossflow system of the water coming from Bolivar reservoir of the same field. In this field La Peña reservoir (upper reservoir) is being depleted naturally and we want to avoid the pressure to fall too far below the bubble point. At the same time the waterflood will be used to sweep the oil from the lower parts of the reservoir toward the wells located in the upper part of the reservoir. The Bolivar reservoir (lower reservoir) has a strong water drive system that has sustained the reservoir pressure in the order of 150 psi below the initial reservoir pressure (3750 psi) for more than 20 years of explotation. Currently exists 1500 psi of pressure difference between these two reservoirs.

In this work we describe the overall project and the several stages to be tested before the full field implementation. We also include the favorable expected economic impact of this method compared to the classic waterflooding. At this moment the laboratory tests have been performed and are explained. Nodal analysis applied to the water production system of the Bolivar reservoir and to the water injection of the La Peña reservoir was performed in order to determine the water rate that will enter into La Peña reservoir. Also the varation of the rate due to the pressure increase in La Peña reservoir with time is considered. Currently we are at the pilot project stage implementation. Field work consists in the workover for the pilot project and is the next operating step. Field tests are part of the next steps and their design are described in detail.
El Tordillo Reservoir Static Characterization Study: El Tordillo Field, Argentina
Authors: Taboada R. , Condat P. , Corsini V. , Mir E. , Conti J. , Fortunato G. , Villivar O. , List D. , Stancel S. , Jones L.
Published: December 2007

The El Tordillo Field is located in the San Jorge Basin, in southern Argentina, and is operated by Tecpetrol S.A.

Realizing this study requires a complex, multi-disciplined approach that allows UTE El Tordillo to describe the reservoir and to develop an appropriate plan to more efficiently use manpower in operating and managing this highly complex reservoir. An essential step toward this goal is developing an integrated structural and stratigraphic model of the reservoirs in the field. These tasks comprise: creating a "living" integrated digital database for the geological, geophysical and mechanical data; making the stratigraphic correlation; identifying all seismically mappable faults and defining the structure of key horizons.

Results of these analyses include the following:

The Reservoirs Characterization Study produced a digital model that is an accurate and detailed 3-D structure and stratigraphic picture of the entire reservoir volume. Specifically, this model provides a consistent, field-wide, stratigraphic correlation of key horizons that were interpreted using with a high level of integration of geologic and geophysical data. The maps show the field wide distribution, structure and well test results for the 241 individual reservoir sands. Another direct benefit of this study is an enhanced understanding of the 3-dimensional distribution of reservoir units and the controls on reservoir quality. These insights will lead to a better understanding of the production compartmentalization of the reservoir and will help UTE El Tordillo optimize and prioritize development and secondary recovery projects.
GRE Composite-Lined Tubular Products in Corrosive Service: A Study in Workover Economics
Authors: Ross Kenneth
Published: December 2007

This paper is a two-part discussion describing Glass Reinforced Epoxy composite linings manufactured and installed in oilfield tubular goods where the material functions as a barrier to corrosion. The paper first focuses on GRE composites in terms of effectiveness and product life compared with less-costly corrosion solutions (such as internal plastic coatings (IPC) and thermoplastic materials like HDPE and PVC). Next, actual case history economic data is presented to qualify the use of Glass Reinforced Epoxy-lined tubular goods over IPC for corrosive seawater injection service in the North Sea. These data are then extrapolated to construct a similar economic model based on workover costs in the Permian basin of West Texas. Additionally, net present value (NPV) analysis can be used to illustrate the saving s in long term operating costs over the life of the project.
Simultaneous Determination of Reservoir Pressure and Initial Fluid-in-Place From Production Data and Flowing Bottom Hole Pressure -- Application
Authors: Wang Shie-Way
Published: December 2007

This work presents procedures on how to apply a newly developed method to simultaneously determine the average reservoir pressure and initial fluid in place using surface production data and flowing bottom hole pressure. This new method is derived from a combination of a generalized material balance formulation and pseudo steady state theory. Reservoir simulation was used to generate production history and flowing bottom hole pressure via hydraulic tables, which were used to calculate average reservoir pressure and initial fluid in place in order to validate the accuracy of this new method. Five examples were investigated for production with vertical and horizontal wells in oil and gas reservoirs at constant rate or constant flowing bottom hole pressure. Calculated initial-fluid-in-place and average reservoir pressures agree very well with that derived from reservoir simulation. This new method is useful in analyzing surface production data in the following conditions: (1) reservoirs significantly lack data, (2) buildup tests are inconclusive in determining average pressure, (3) buildup tests are expensive or difficult to run such as wells in tight and over-pressured reservoirs or with subsea completion.
Numerical Well Test Analysis of Stress-Sensitive Reservoirs
Authors: Pinzon Claudia L. , Chen Her-Yuan , Teufel Lawrence W.
Published: December 2007

Two issues are addressed in this study: (1) What are the characteristics of the well testing responses if the reservoir is stress-sensitive? (2) How accurate are the well-test-estimated permeability and drainage volume using the existing techniques (non-stress-sensitive assumption) if the reservoir is stress-sensitive? We study the above issues using a fully coupled fluid-flow/geomechanical simulator. Numerical transient pressure and reservoir limit tests are presented to illustrate the differences between cases of (i) constant reservoir properties and (ii) stress-dependent reservoir properties. Case (ii) assumes that the permeability is a function of effective stress, which in turn is constantly changing during the well-test period. Characteristics of pressure derivatives are also presented to extend current well-test diagnosis techniques into stress-sensitive reservoirs. The total (or system) compressibility is shown to be extremely critical in the estimation of the drainage area and volume. An all-purpose "rock compressibility" is proposed to represent the rock compressibility term in the total compressibility.
Alteration of Reservoir Wettability Due to Asphaltene Deposition in Rhourd-Nouss Sud Est Field, Algeria
Authors: Amroun Hacene , Tiab Djebbar
Published: December 2007

Wettability is an important factor in a number of petroleum production processes including secondary recovery and tertiary recovery operations. In fact these processes in the later life of the reservoir are more or less controlled by the wetting properties of the rock and fluids present in it.

The role of Asphaltene deposition on the wettability is investigated in this research work. It has been observed that the Asphaltene deposition has a strong role in wettability reversal. Among many factors, the high molecular weight with, polar fraction of crude oils, including the asphaltenes, are considered to be the primary wettability altering agents. Considering the complexity of reservoir rocks and crud oils, each reservoir system is a specific case and its behavior can only be confirmed through experimental work.

In this paper the role of asphaltene and its deposition in altering the reservoir wettability of Rhourd-Nouss Sud Est (RNSE Algeria) field is presented. It was found that the samples of RNSE are of intermediate wettability and are very close to neutral wettability. At higher concentrations of asphaltenes in the crude oil the rocks have greater tendency to become neutral-wet systems.