bluuebunny/crossref_metadata_2025 huggingface dataset:
The Integration of Petrophysical Data for the Evaluation of Low Contrast Pay
Authors: Deakin Mark , Manan Wan
Published: December 2007

To date eight gas/condensate fields have been discovered through exploration and appraisal drilling by Carigali Triton Operating Company Sdn. Bhd., Operator of Block A-18, JDA on behalf of its Shareholders Petronas Carigali (JDA) Sdn. Bhd., Triton Oil Company of Thailand (JDA) Ltd., and Triton Oil Company of Thailand Inc., Contractors to the Malaysia-Thailand Joint Authority (MT JA). Sequences 0-II of these fields include stacked shaly sand' reservoirs containing low contrast pay. The suppressed resistivities of these reservoirs are caused by cm-dm clay distributions, which vary between facies, making the identification and quantification of reserves difficult.

An integrated petrophysical approach has been adopted to overcome these difficulties. Borehole image-log interpreted facies are treated as classes of clay distribution, and the log responses of each facies are calibrated to core data, acquired separately for each facies. Saturation-height functions are used with wireline formation pressures to project initial conditions capillary pressure saturations into all cored intervals, providing foot by foot log independent gas volumes. For each facies, the log data and Waxman Smits equation are calibrated to these gas volumes through the saturation exponent (n *) The role of n* as a core-log matching parameter is analogous to apparent fluid density in a core-log porosity evaluation. In addition, gamma ray is used to optimize n* for each facies. Results are supported by the fluid mobility seen on limited magnetic resonance logs, and all other available data.

The technique provides a simple, reliable and inexpensive means to evaluate the hydrocarbon potential of low contrast pay. The determination of formation water resistivity (Rw) is circumvented and data acquisition costs are minimal as the required data has often been acquired for other purposes. In this case study its application will result in a gas reserves up-grade for CTOC, its Shareholders and the Malaysia-Thailand Joint Authority.

P. 327
Profitable Continuous Flow Gas Lift in 18,000 Feet TVD Wells with Low Reservoir
Authors: DeMoss Ed , Ruiz-Garcia Saul , Sarmiento-Mendoza Salvador , Perez-Fuentez Alfredo , Gossell Steve
Published: December 2007

Two fields near Villahermosa, Tabasco, Mexico, have been difficult to produce with gas lift because they are so deep and the reservoir pressure is so low. In both fields 1000 psig lift gas systems were installed several years ago and served effectively for several years. To get a higher lift gas pressure with today's low reservoir pressures, skid mounted motor compressors were installed at ten well sites in 1995-96. Sixteen more compressors were installed in 1997.

In one field, Cardenas, the static pressures and depths range from 2794 psig at 18446 ft to 2712 psig at 18056 ft. This field has twenty-two wells and produces 37,500 bopd. Six wells were gas lifted with the 1000 psig lift gas system. In 1995-96, four compressors were installed at four of these six wells and the production increased 5258 bopd.

The other field Samaria-Iride, has a static pressure of 3342 psig at 14750 ft. This field has fifty wells and produces 107,850 bopd. Twenty-nine wells were gas lifted with the 1000 psig lift gas system. In 1995-96, six compressors were installed at six of these twenty-nine wells and the production increased 6595 bopd.

All of the designs were made with a kick off pressure of 2300-2500 psig using API type IPO valves for unloading. The body of the paper discusses two wells from each field describing the before and after production and the completion schematic.

P. 135
Field Electrification Efficiencies: One Operator's Experience in the Conger (Penn)
Authors: Harris B.W. , May K.R.
Published: December 2007

Several strategies have been employed in Wagner & Brown's Conger field of over 500 beam-pumped wells to reduce electrical power bills. The first involved a decision, early in development, to deliver the highest practical voltage to each wellsite. Later, as well count reached into the hundreds, full understanding of the distribution system, its power flow and line losses, required computer modeling of a combined electrical system that was previously metered by two separate primary meters. That modeling brought about elimination of power factor penalties and reduction of IOR power losses by optimum placement of capacitors.

By coordinating the system protection devices such as primary fuses and upstream reclosers, the system reliability was improved and the production downtime was reduced.

Placement of a digital PME with memory and computer download capability allowing scrutiny of field power usage in 15 minute increments led to overall power demand (KW) leveling and reduction of peak demand through installation of digital pump-time clocks. Current utility deregulation promises significant cost reductions for users flexible enough to alter or otherwise control the way in which they consume electricity.

P. 149
Squeeze Cement Matrix Improves Communication, Increases Efficiency, and Reduces
Authors: Lopez Henry , Renshaw Dave
Published: December 2007

The Wickett Field in the Permian Basin, located 40 miles West of Odessa in Ward County, Texas, is a mature field where squeeze operations occur approximately once per week on each workover rig. Historically, squeeze designs and success ratios have been evaluated individually on a "job by job" basis; this has maintained squeeze cementing costs at a very high level for both the operator and the service company. These costs can include factors such as initial and repeated cement laboratory testing on varying cement slurries, on-site pumping services, cementing additives, surface and down hole equipment, administrative and engineering time of both the operator and service company personnel, rig time, and repeated costs with each squeeze attempt.

For some operators, additional factors can contribute to the complexity of this process such as limitations on a consistent methodology or organized approach to the operational aspects of a squeeze operation. Variations can exist within engineering, field supervisory, and service company personnel as to proper on-site pumping techniques, cement slurry design, or necessary volumes of cement for initial or subsequent attempts. Often times, a very limited established or organized method is in place for "looking back" on the success or failure of any particular cement slurry or operational technique. Finally, an overwhelming amount of selections are available in the design process concerning slurry design and operational techniques.

We will show how an operator, in close association with a service company can establish specific guidelines to manage these complex variations. We will present the methodologies that have reduced the complexity and increased the manageability of an ongoing process. Through these efforts, laboratory testing, administrative and engineering time commitment by the operating and service company personnel, and overall costs in remedial squeeze cementing have been reduced. In addition, these methodologies have improved communications, helped standardized operational considerations, and have increased the probability of successful squeezes on the first attempt.

P. 155
New Exact Spherical Flow Solution With Storage for Early-Time Test Interpretation
Authors: Proett Mark A. , Chin Wilson C.
Published: December 2007

Conventional methods used to analyze early-time formation transient test data are approximate and do not model the entire timewise pressure response. Alternatively, detailed models used for early-time storage or late-time analysis are numerical and chart-oriented, and not amenable to simple physical interpretation. In this paper, the general spherical flow formulation, with wellbore storage, is solved by inverting the Laplace transform to produce a closed-form analytical solution. This new solution reduces to previously published early- and late-time solutions in the respective asymptotic limits. Importantly, the availability of the new solution permits convenient pressure-response-to-theory-matching using the complete time regime (early-, transitional-, and late-time data), rather than the typical late-time matching to the asymptotic limit of the spherical flow regime. The new solution also allows accurate formation evaluation using early- and intermediate-time data only, thereby reducing rig down-time required for testing.

The new analytical solution is derived for the full initial- boundary value problem for transient, compressible, spherical flow using Laplace transforms. In this paper, the Laplace transform is inverted to obtain a closed-form expression for the pressure field, and additionally, expressions for pressure derivative and sandface flow rate are derived in terms of the complex error function. These solutions are compared to existing numerical solutions obtained by approximate transform inversion, and to finite element model results that include the three-dimensional effects of wellbore geometry. The accuracy and interpretation speed of the new solution permits systematic determination of all flow parameters, to include storage coefficient, formation fluid compressibility, permeability, and pore pressure. It circumvents limitations inherent in existing methodologies, e.g., where parameters such as compressibility are assumed a priority.

A new type of drill stem well test tool is also described, and the new solution is used to analyze its field test data. Wireline tester log data examples are analyzed to illustrate the utility and power of the new solution. The examples are used to demonstrate how the new solution saves rig time by using convenient, microprocessor-based, real-time regression analysis to determine formation properties.

P. 167
Analysis of Wireline Formation Test Data from Gas and Non-Darcy Flow Conditions
Authors: Kasap Ekrem , Lee Jaedong
Published: December 2007

In addition to fluid samples, formation testers provide undisturbed formation pressure (p*), as well as mobility and compressibility of formation fluids, essential for estimating initial hydrocarbon in place and recovery efficiency.

Formation tests provide in situ measured permeability and permeability profiles. Recent advancements have been reported in interpretation of pressure test data on liquid saturated formations. For gas formation, however, both compressibility and viscosity are strong functions of pressure; therefore, they are variables during the test. Appreciable temperature change is also observed during gas formation testing. Large gas compressibility and much smaller gas viscosity complicate the analysis. Moreover, gas flow is complicated by non-Darcy flow effects.

In this study, the Gas Formation Rate Analysis (GFRA) technique is developed to analyze gas pressure tests. We calculated gas pseudo-potentials and analyzed variation of pseudo-potential versus formation rate during a formation test by utilizing the geometric factor concept. Forchheimer's equation has replaced Darcy's equation to study non-Darcy flow effects.

The technique is applied to a field test, from which mobility is obtained. The results of the technique are verified by history matching a field test with a 3-D near wellbore simulator, developed for gas formation testing modified for non Darcy flow effects.

P. 183
Porosity Determination in Gas-Bearing Formations
Authors: Quintero Luis F. , Bassiouni Zaki
Published: December 2007

The porosity of gas-bearing formations is determined using empirical models. These models use the porosity values displayed by the density and neutron logs, assuming that both tools investigate the same gas saturation profile. They also assume that the variation of gas density and mud filtrate saturation and salinity has little effect on porosity values. These assumptions could introduce a high degree of uncertainty, specially in case of tight gas sands.

A new model is proposed which uses the density porosity value and a neutron porosity value derived from the reading of the near detector. The model incorporates a parameter depending on the gas density and drilling fluid saturation and salinity. A forward model establishing the neutron and density tool responses under a known set of conditions was used to assign values to this parameter. The inverse model derives the needed porosity values.

In addition to providing a more representative porosity value for gas-bearing formations, the model can also be used to determine the bypassed gas saturation in the flushed zone of the formation. The value of the bypassed gas saturation is used as an indication of the displacement efficiency in water- drive gas reservoirs.

P. 213
CO2 Energized and Remedial 100% CO2 Treatments Improve Productivity in Wolfcamp Intervals, Val Verde Basin, West Texas
Authors: Johnson Raymond L. , Walters Wallace W. , Conway Michael W. , Burdett Bruce S. , Stanley Rod G.
Published: December 2007

Fluid clean-up effects have hampered stimulation success in many tight, naturally fractured sandstone reservoirs. The petrophysical responses of treatment fluid invasion can affect short-term and in some cases long-term reservoir deliverability. Many times reservoirs such as the Wolfcamp intervals, in the Val Verde Basin of west Texas, exhibit better response to CO energized fluids than non-energized fluids. We will present data from a case study of several wells in the Wolfcamp A, C, and D intervals where CO-assisted fluid and 100% CO treatments have significantly improved productivity in both initial and remedial applications.

First, we will include case histories where CO-assisted fluid fracturing and refracturing treatments improved performance over non-energized, fluid treatments, Next, we will describe cases where injections of non-energized fluids systematically reduced production; in particular we will describe a case that was successfully remediated by a 100% CO treatment. Then, several cases will be presented showing sustainable improved responses following 100% CO treatments in previously energized and non-energized fracture stimulated intervals.

P. 255
Development and Field Application of a Delayed Breaker System for Use at High
Authors: Much Michael G. , Franklin Vernon L.
Published: December 2007

It can be difficult to effect a timely fracturing fluid break, after a hydraulic fracturing treatment, in reservoirs above 190 F. Fracturing fluid systems often are quite stable at temperatures up to 300 F. At elevated temperatures the treatment designer is faced with the selection of a fracturing fluid breaker from three main categories: oxidizers, acids and enzymes.

Typical oxidizing breakers systems, used at temperatures up to 250 F, are persulfates often encapsulated by a thin film of polymer. Encapsulated persulfates often "leak" allowing some of the encapsulated breaker to be rapidly released into the fracturing fluid. Early release of oxidizing breaker degrades the fracturing fluid during the fracturing treatment—before the desired time.

Acids can be used as breakers but are usually limited to lower temperatures. In addition, the buffering capacity of the formation and the fracturing fluid can significantly impact the performance of acids and finally, acids are usually less cost effective than other breakers.

Polymer specific enzymes, while an effective breaker at elevated temperatures, do not provide a rapid break in fluids with a high pH.

The industry has developed an appreciation of minimizing gel loadings in fracturing fluids because of perceived high insitu polymer concentrations brought about during fracture closure. For this reason, it is desirable to use breaker systems that do not prematurely attack fluid viscosity, allowing use of the minimum gel loading that adequately transports proppant

A high temperature, fracturing fluid breaker system that circumvents many of the problems discussed has been developed. The breaker system, instead of relying on a micro-thin coating on a very reactive substrate, provides a different approach to the problem. The alternative breaker system discussed here utilizes a non-encapsulated, oxidizing breaker that effects a delayed break by slowly releasing free radicals in water based fracturing fluids, thus degrading fracturing fluids in a controlled manner.

P. 273
Find Grid CO2 Injection Process Simulation for Dollarhide Devonian Reservoir
Authors: Wang Shie-Way , Robertson Steven D.
Published: December 2007

Carbon dioxide injection in the Dollarhide Devonian reservoir commenced in May 1985. Subsequently, CO injection was expanded to an area of the majority southern fault block. As of May 1995, CO injection has been implemented in the entire Devonian formation in five phases. Hybrid CO injection was chosen to be the primary mode of operation. During the course of this project, the operator experienced reduction in injectivity when switching to WAG after injecting a 10% hydrocarbon pore volume CO slug in phases 1 and 2. Oil production consequently decreased due to reduced injectivity. This study was designed to answer operation related questions. We selected a 5-spot pattern in the southern fault block for this study partly because it had the longest production history with hybrid CO injection, and also because the study area was not complicated by faults. Forecasts were made over a period of twenty years for four scenarios. The cause of sustained high water cut at the central producer was also investigated. A fine grid model was used in this study in order to compare more accurately the recovery efficiencies between a single CO slug and hybrid CO injection, and to investigate the advantages of operating at a lower pressure.

P. 319
Gel Treatments for Reducing Channeling in Naturally Fractured Reservoirs
Authors: Seright R.S. , Lee Robert
Published: December 2007

This paper considers some of the reservoir variables that affect the severity of channeling and the potential of gel treatments for reducing channeling through naturally fractured reservoirs. We performed extensive tracer and gel placement studies using two different simulators. We show that gel treatments have the greatest potential when the conductivities of fractures that are aligned with direct flow between an injector-producer pair are at least 10 times the conductivity of off-trend fractures. Gel treatments also have their greatest potential in reservoirs with moderate to large fracture spacing. Produced tracer concentrations from interwell tracer studies can help identify reservoirs that are predisposed to successful gel applications. Our simulation studies also show how tracer transit times can be used to estimate the conductivity of the most direct fracture. The effectiveness of gel treatments should be insensitive to fracture spacing for fractures that are aligned with the direct flow direction. The effectiveness of gel treatments increases with increased fracture spacing for fractures that are not aligned with the direct flow direction.

P. 419
North Dakota's Lodgepole Play: A Look at the Reservoir and Producing Characteristics
Authors: Young Susan W. , Caamano Edward , Jackson Darron B. , Morgan Wiliam A. , Sheedlo Mark K. , Ahr Wayne M.
Published: December 2007

In 1993, Conoco discovered the first commercial hydrocarbon reservoir in Lodgepole Waulsortian mounds in North Dakota, Delineation, based on 2D seismic and proximity to successful wells, and then unitization of the Dickinson Lodgepole Unit (DLU), quickly followed. Conoco and other operators acquired several 3D seismic surveys in and around the Dickinson area following the discovery. However, the play did not expand until almost two years later, when Duncan Oil completed a second Lodgepole discovery just three miles from the DLU.

The Dickinson area now has nine productive Lodgepole fields. This has been a highly competitive play, because the lP of a Lodgepole well can exceed 1000 BOPD, usually water-free, and individual wells can produce more than 1 million barrels of oil.

Production is from low porosity (5%) Waulsortian mounds, which range between 250 to 320 ft. thick and have oil columns up to 180 ft. These reservoirs have a heterogeneous internal architecture, related both to original depositional geometry and facies, as well as diagenetic alteration. The mounds in the Dickinson subsurface have been through multi-stage diagenesis and fracturing, which has created an excellent dual porosity system. The mounds' internal architecture is therefore difficult to predict. However, the location and gross morphology of the mounds can be determined fairly well from 3D seismic, which is a very good tool for both exploration and development.

These reservoirs are excellent candidates for secondary recovery. All of the Dickinson area Lodgepole reservoirs are either currently under waterflood, or are in the process of being unitized so that water injection can begin in the near future, Primary recovery has been estimated at approximately 28%, and secondary recovery is likely to be 13% or higher. With total original oil-in-place estimates of 70 to 100 million barrels for the Dickinson area mounds, the Lodgepole presents a very attractive exploration target.

P. 441
West Welch CO2 Flood Simulation with an Equation of State and Mixed Wettability
Authors: Taylor A.R. , Hinterlong G.H. , Kumar K.H.
Published: December 2007

This paper describes the reservoir engineering aspects of the CO feasibility study for Department of Energy Class II project, at the West Welch San Anders Unit. The DOE Class II demonstration simulation effort for the CO feasibility study uses an 11 component equation of state (EOS) for surface facility design. Relative permeability data measured in the laboratory indicated two different waterflood residual oil saturations. The low reservoir temperature causes the fluid phase behavior to exhibit a two liquid hydrocarbon phase region with CO present Fluid characterization steps taken to virtually eliminate the two liquid hydrocarbon phase region is described. The problems these changes created and adjustments made to the EOS to improve the simulation are reviewed. We show that the EOS needs to predict slim tube recovery compositions as well as the total slim tube recovery to adequately predict field scale oil recovery. The fluid characterization procedure, described here, made the full field simulations more closely match field CO recovery.

Two types of wettability were identified from relative permeability curves at the project in the Welch field. The intervals of different wettability were identified from resistivity logs to aid in placing these intervals in the proper model layers. The geologic model with both relative permeability rock types led to overpredicting oil recovery. However, the low waterflood residual oil saturation appears more significant in the higher permeability rock. Thus, the relative permeability tests from core samples with higher permeability led to significant differences in model results. Subsequent history matching efforts, incorporating 3D seismic, showed that the relative permeability rock type with low residual oil saturation to water was not volumetrically significant. A separate paper, SPE 39809, describes the incorporation of 3Dseismic into the geologic model.

P. 489
Enhanced Reservoir Characterization Using NMR Core and Well-Log Derived Data
Authors: Elgagah Shedid A. , Tiab Djebbar , Osisanya Samuel O.
Published: December 2007

The purpose of this study is to develop new models capable of providing better description of the reservoir through the use of the concept of Reservoir Quality Index (RQI) combined with the available permeability models appearing in the literature.

Six enhanced reservoir characterization models have been developed that incorporate core and/or conventional well-logging derived-data to identify hydraulic (flow) units. Two models are developed based on equation of Nuclear Magnetic Resonance (NMR) to identify flow units using core data. In addition, three flow unit models are developed based on Timur, Wyllie and Rose, and a generalized permeability equations. The sixth model is developed using Jorgensen permeability equation. It is found that each flow unit can be represented by a straight line on a log-log plot of the RQI versus porosity,, or versus the parameter()depending upon the permeability equation used.

The straight line (representing the flow unit) yields various unique slopes for the different models. This depends upon the porosity exponent that appeared in the permeability equation. In addition, each flow unit model possesses a characteristic intercept on the NMR Decay time- # log-log plot, or on the RQI- # log-log plot, or on RQI() log- log plot. The new flow unit models are validated by using actual and simulated data. Use of the new models in combination with the systematic technique developed,

2. Is correlative and mappable at the interwell scale; represents effctive tools for enhancing reservoir characterization.

P. 505
A New Empirical Correlation to Predict Apparent Viscosity of Borate-Crosslinked Guar
Authors: Goel Naval , Subhash Subhash N. , Asadi Mahmoud
Published: December 2007

Successful design and completion of the hydraulic fracturing treatments depend on accurate estimation of fracturing fluid viscosity under in-situ conditions. However, the viscosity of the widely used borate-crosslinked guar gel is extremely difficult to measure due to its dependence on temperature, wellbore shear pre-conditioning, fracture shear rate, and pH. Furthermore, these properties require that the fluid mixing, pumping, and characterization to be performed under representative field conditions. Because of these complexities, there is no reliable correlation available in the literature to relate borate-crosslinked guar gel viscosity with its dependent properties. Therefore, in the present study, borate-crosslinked guar gel rheology measurements, obtained with a field scale High Pressure Simulator (HPS), are used to develop a correlation.

The empirical correlation is developed on the basis of method of reduced variables, whereby shear stress-shear rate data at different temperatures are combined into one curve at a reference temperature T. Present study extends this method to include the effect of shear history on the rheology of guar polymer crosslinked with borate ions In the paper, this technique is used to generate master curves of reduced apparent viscosity-shear rate for borate-crosslinked guar at each pH. Furthermore, the developed empirical equations relate apparent viscosity of crosslinked guar to fluid temperature, shear history and shear rate.

The developed correlation is presented in a simple form. The correlation will be helpful for comparison of model calculated values with the laboratory measured viscosities, as the laboratory values are not supported by a field scale fluid characterization equipment.

P. 551
Fluid Sampling from Damaged Formations
Authors: Lee Jaedong , Kasap Ekrem
Published: December 2007

A high quality formation fluid sample is essential to identify the composition of formation fluids which is required in designing expensive production facilities. Formation fluid samples are also needed to assess hydrocarbon reserves and reservoir recovery efficiency.

Minimal contaminant is desired in formation fluid samples for proper composition and PVT analyses. The contaminant is the drilling fluid filtrate that invaded near wellbore formations during and after the drilling process. The filtrate in the sample compromises sample quality by reducing usable sample volume and altering its composition and PVT properties. To sample clean enough formation fluid, a certain volume of fluid must be pumped out prior to sampling. Although initially a mixture of invading filtrate and formation fluid is produced, generally clean enough formation fluid is sampled after a certain fluid volume is pumped out.

The objective of this study is to identify the controlling parameters in determining the optimum pump out volume. After a certain pump out, a minute increase in sample quality requires long pump out times. Therefore, pre-job planning to obtain pump out volume and duration of pump out required, based on the sample quality, is important for the tool and hole safety.

Finite element simulations with realistic wellbore, formation geometry and mud cake characteristics are run to study the effects of pumping rate, invaded zone thickness, damaged zone permeability, formation anisotropy, and mud cake quality. The simulation results indicate that pump out volume, not pumping rate, controls sample quality. Formation damage and anisotropy improve sample quality by limiting the production from the invaded zone. Poor mud cake quality and deeper invaded zones have adverse effects on sample quality and require more careful planning.

P. 565
Scaling Parameters for Characterizing Waterflood Recovery from Anisotropic Matrix Blocks in Naturally Fractured Reservoirs
Authors: Bujanos Jose Luis Sanchez , Miller Mark A. , Sepehrnoori Kamy
Published: December 2007

A study was conducted to simplify the modeling of countercurrent imbibition matrix-fracture transfer flow for dual porosity modeling of naturally fractured reservoirs. Through both analytical work and detailed numerical simulations, scaling studies were conducted of two-phase countercurrent imbibition problem in 3D anisotropic matrix blocks. The ninin result of the work was to identify four key parametric groups which control countercurrent imbibition. This result would not only lead to additional insight into how parameters interact to govern countercurrent imbibition during waterflooding, but would also simplify and aid simulations involved in sensitivity studies, history matching, and stochastic studies. Application of the parametric groups to field-scale dual porosity modeling is also shown.

P. 61
Automatic Synchronization of Electric Generators Based on PLC's
Authors: Rivera Abelardo
Published: December 2007

Pemex Exploracion y Produccion offshore marine platforms are located in the Gulf of Mexico. Inhabited platforms need electric energy to operate their processes and motors. This energy is supplied by motor generators and turbo generators. Typically, a marine platform has 2, 3 or more generators to always have electric energy available. The motor generators and turbo generators have a control system where operating personnel can start, stop and parallel them. Parallel generators mean to connect 2 or 3 generators to the same bus. The energy supplied to the bus is divided among the paralleled generators and each generator supplies energy proportional to its maximum capacity. The greater the capacity, the greater the energy it supplies. Most electric generator systems are stoped, started, and paralleled manually, but some systems have changed to automatic control systems based on Programable Logic Controllers (PLC).

P. 109
The Rejuvenation of Two Gas Basins in Mexico: Burgos and Veracruz
Authors: Guzman A.E. , Yanez-Mondragon M.
Published: December 2007

Demand for natural gas in Mexico is expanding. This increase in the use of gas is due to a rapidly developing household market and to substitution with gas of heavy fuel oils for industrial uses. Increasingly stringent environmental standards are incentivating this demand. Pemex Exploration and Production, as the government agency responsible for finding, developing and producing Mexico's oil and gas resources has implemented strategic projects to fulfill the growing need for gas supplies. This presentation gives an overview of the actions that Pemex E & P has and is taking in the Burgos and Veracruz basins to help satisfy the nation's need for gas.

Both Burgos and Veracruz are tertiary siliciclastic basins located in the western margin of the Gulf of Mexico proper, and both are producers of dry sweet gas. Burgos is located in northeastern Mexico, it covers 49,800 km2. It is limited to the west and south by east diping mesozoic marls and limestones, to the east by the continental slope and to the north by the Rio Bravo del Norte (Rio Grande River), although the basin itself continues into South Texas, where it is known as the Rio Grande Embayment (Texas Railroad Commission, District IV). The Veracruz basin with an areal extent of 18,000 Km2 is located on east central Mexico and is limited to the west by a laramide thrusted foldbelt (producer of sour wet gas, condensates and some oils), to the north by recent volcanic rocks, to the east by the continental slope and to the south it becomes the Isthmus Saline basin. Dry gas production reached a maximum of 620 MMcfd in 1970 for Burgos and 45 MMcfd in 1971 for Veracruz.

P. 115
Design of a Two Piece Lifted jacket for 630 Foot Water Depth
Authors: Dorgant Paul L.
Published: December 2007

A new type of jacket design was developed for a Gulf of Mexico platform in 630 feet of water. The jacket was designed for installation in two sections that were joined underwater with a grouted connection. Both jacket sections were lifted from transport barges and installed on location with a Semi-Submersible Construction Vessel. This installation method was used to avoid the typical launch framing required for jackets in this water depth. This launch framing accounts for approximately 20% of a typical launched jacket weight. The jacket fabrication schedule is also reduced due to less steel tonnage. This paper describes the unique features and important aspects of the design, including the design approach, the underwater mating and the splice details. The development of this design concept has added an alternative to conventional single piece launched jackets designs for water depths from 500 to 700 feet. Information provided in this paper will allow designers and planners to evaluate this alternative design concept. Results are presented showing the steel weight savings.

P. 195
Analysis of Two-Phase Flow in Horizontal and Inclined Pipes With Mechanistic Models
Authors: Granados-C Jaime , Camacho-V Rodolfo
Published: December 2007

A computer program has been developed for simulating twophase flow in horizontal and inclined pipes. This program is based on the mechanistic model of Xiao et al., extending the inclination angle from + 150 to the range + 45 using the works of Barnea and Hasan and Kabir.

With this hybrid model it is determined the flow pattern, under stationary conditions, and hydrodynamic characteristics of the flow pattern, mainly hold-up and pressure gradients.

An analysis of synthetic information, generated with the computer program, has been done. Based on statistical parameters, the mechanistic model performance has been compared with that of Beggs and Brill correlation, observing similar trends, with both procedures for the whole range of pipe inclination angles.

Finally, through 3-D graphs, performance of principal hydrodynamic parameters has been presented.

P. 221
Performances of Transient Two-Phase Flow Models
Authors: Lopez D. , Duchet-Suchaux P.
Published: December 2007

This paper was prepared for presentation at the 1998 International Petroleum Conference and Exhibition of Mexico held in Villahermosa, Mexico, 3-5 March 1998.
BARBOX: A Technical and Economical Viable Alternative Concept for FPSO System
Authors: Ho Rong-Tai , Bayazitouglu Yildirim
Published: December 2007

Brown & Root's BARBOX concept is an alternative, purpose-built, deep-draft monohull system for floating production, storage, and offloading (FPSO). This FPSO system concept has been designed for worldwide applications including West Africa, the North Sea and the Gulf of Mexico environments. The BARBOX's stiffened flat plate construction gives it a low capital investment cost compared to systems with minimum water plane hull types (e.g.. semi-submersible, SPAR, TLP) and ship-shaped FPSO. The BARBOX's dynamic motion characteristics are similar or better than those of comparable ship-shaped FPSO configurations. This paper also considers construction of the BARBOX hull in the Gulf of Mexico region. A recent Brown & Root study indicated that the Gulf coast fabrication yards were technically capable to fabricate the BARBOX hull and they could be cost competitive against worldwide shipyards.

P. 249
Design and Application of Passive Fire Protection for the Decks of Deepwater Tension Leg Platforms
Authors: Hunt R.J.
Published: December 2007

As an integral part of the platform's emergency response procedures, passivefire protection (pfp) has been designed for the decks of the Mars, Ram/Powell& Ursa Tension Leg Platforms which lie in the deepwater Gulf of Mexico.

The area and thickness requirements for the pfp coating are developed for the primary deck steel on each of the platforms. The design process is described in detail, from the defmition of the fire scenario to the treatment of the fire's heat flow characteristics and the application of data representmgsteel properties at elevated temperatures. Optimization of the area of primarysteel requiring protection is discussed with reference to ultimate strengthanalysis which is used to ensure that the pfp coating is applied for maximum effect.

The quality of the application process at the fabrication facility has been identified as a fundamental component in achieving the specified level of protection. Key issues concerning the application of the pfp material have been identified and are presented as criteria established to aid in the selection of a fire proofmg material.

The application of the pfp coating represents a substantial amount of work in the fabrication process and as such has the potential to significantly affect the fabrication schedule. Details of experience gained from the successful application of the fireproofing material on three major projects are presented.

P. 257
Integrating Modern Open Hole Logs, Core Data And Old Electric Logs: A Study Of The San Andres Field, Veracruz, Mexico
Authors: Pursell David A. , Hunt Ercill R. , Trevino Alfredo
Published: December 2007

This paper describes methods and results of integrating modern openhole well logs and core data with old electric survey logs (ES) to determine porosity, water saturation, and net pay thickness for more than 240 wells in the San Andres Field, Veracruz, Mexico. A majority of the wells were logged with the old ES logs. As field development continued, modern resistivity logs and porosity logs were run. Several relationships were developed which allowed the old ES logs to be analyzed and the results incorporated into the reservoir description. Specifically, relationships were developed to determine porosity from the old neutron logs (GNT - both count rate and API scales), and to determine true formation resistivity (Rt) using the 64" normal logs. Log calculated porosity and water saturation were verified with available core results.

P. 267
Evaluating and Monitoring Reservoirs Behind Casing With a Modern Pulsed Neutron Tool
Authors: Simpson G. , Jacobson L. , Salazar F.
Published: December 2007

Pulsed neutron capture logs have long provided a means of determining water saturation and estimating porosity of formations behind casing. Recent technological advances in pulsed neutron logging have resulted not only in improvements in saturation and porosity data, but also in the capability to provide information regarding water entry and flow, lithology, and improved differentiation of gas-filled zones from tight formations. These advances provide greater accuracy in reservoir evaluation and monitoring as well as improved completion and production diagnostics.

Inelastic, capture, borehole, and background spectra are now utilized to enhance porosity estimates, identify water flow, and help determine lithology. Modular tool design allows the pulsed neutron tool to be combined with production logging tools for more reliable production diagnostics. Simple tool modifications permit quantitative measurements of water velocity and borehole oil holdup. The modular design also allows additional detectors to be placed in the toolstring for lithology identification and gravel pack evaluation.

This paper discusses this new pulsed neutron capture technology and gives an overview of the expanded range of pulsed neutron applications. Field examples of waterflow detection, gravel pack evaluation, oil/gas discrimination, and conventional analysis are presented from offshore wells in the Gulf of Mexico and from onshore wells in Mexico and the U.S.
Identifying and Analysis of Key Variables at the "Terminal Maritima de Dos Bocas", Using Statistical Process Control.
Authors: Vazquez-Martinez A. , Melo-Gonzalez R. , Rodriguez-Chiquito V.M.
Published: December 2007

A case of identifying and analysis of key variables into a crude-oil reception, conditioning and distribution station using Statistical Process Control Techniques (SPC), is presented. The station identified as "Terminal Maritima de Dos Bocas" (TMDB), situated near the town of Paraiso in the SouthEast Mexican state of Tabasco, receives eight crude lines from Campeche offshore plataforms and some South land-reservoirs, moreover it conditioning and distributes crude-oil for international and domestic commerce.

Owing the high international markets crude-oil competition and its respective demand of more strict conditions of quality for it commerce, it is neccesary to incorporate new technologies to the terminal looking for satisfying present and future needs. To do this, it was primary important to make a review of the process and proceedings in the terminal driven, with the objetive of identify those variables with high influence on its products quality and which determines it (i.e. Key Variables). We follow the methodology of Statistical Process Control to find out this key-variables and to quantify the benefits we should have for the implementation of such tehcniques as first step to the general application of the methodology in real time.

P. 301
Modeling and Optimizing Oil and Gas Production and Gathering Systems: Cerro Fortunoso Field Case
Authors: Galliano G. , Degiorgis G.L. , Lopez M. , Fornes A.
Published: December 2007

Cerro Fortunoso is one of the main fields of YPF Mendoza Business Unit. Itcurrently produces more than 7,500 bbl fluid/d from a hundred wells, most of them on sucker rod pumping. The field is located 80 miles from the nearest town, near the Andes Mountains and the environment is quite hostile windy, cold and with frequent snowfalls). Besides the field is very near a National Park.

Produced fluids are usually a problem. The oil is heavy (14.7 API) and viscous (more than 3,000 cp at ambient conditions). It tends to form emulsions with production water and behaves as a non newtonian fluid below 120 F.

The produced gas contains about 95 % of CO2 and has been vented up to now. In late 1996 a decision was made to reinject the produced gas in order to maintain pressure and prevent environmental damage.

A small technical team used a complex network simulator to model both the current field oil gathering and the future gas reinjection systems. Although the model fitted experimental data successfully and proved to be a powerful design tool some limitations to the simulator were found.

Due to the fact that commercial simulators do not take into account non-newtonian performance. a parallel study was conducted to analyze the effect of this behavior on predicted pressure drop. The team concluded that although deviation was found to be slight, non- newtonian effect should be properly included on design calculations.

As the gas will be reinjected at field conditions near its critical point. thermodynamics becomes extremely important. Five different thermodynamic software packages were run to predict gas phase envelope. Important differences between some models were detected.

P. 307
Unstable EOR Displacements and Their Prediction Using the Karhunen-Loeve (K-L) Decomposition
Authors: Gharbi R.B. , Smaoui N. , Peters E.J.
Published: December 2007

The paper describes a novel approach to model unstable fluid displacements in porous media. The approach is based on the Karhunen-Loeve (K-L) decomposition which is able to predict the fluid distributions of miscible displacements inside a porous medium. Several first-contact miscible displacement experiments, each with different fluid properties, were conducted, and the fluid distributions inside the porous media were mapped at various times using nuclear magnetic resonance imaging (NMRI). The K-L decomposition is described to identify the coherent spatial structures from spatio-temporal patterns arising from these experiments. It was found that these complex spatiotemporal behavior can be successfully described by few dominant eigen functions. The technique is based on the diagonalization of the covariance or two-point correlation matrix. The K-L decomposition provides information for the successful prediction of Enhanced Oil Recovery (EOR) processes.

P. 341
Numerical Simulator to Analyze Short Build-up Pressure Tests.
Authors: Galindo-N. Agustin , Gonzalez-G. Jose , Camacho-V. Rodolfo , Fairuzov Yuri , Fuentes N. Faustino
Published: December 2007

This paper was prepared for presentation at the 1998 SPE International Petroleum Conference and Exhibition held in Villahermosa, Mexico, 3-5 March 1998.
Analysis of Capillary Pressure Effects on Well Tests in Solution Gas-Drive Reservoirs
Authors: Tellez-C. Guadalupe , Camacho-V. Rodolfo
Published: December 2007

The effect of capillary pressure on well test is investigated. Solution gas-drive, homogeneous and naturally fractured reservoirs are considered. A numerical simulator, with a Warren and Root formulation for the case of fractured reservoirs, is used to generate synthetic data.

For homogeneous reservoirs the procedures of Perrine-Martin and pseudo-pressure are evaluated under the presence of capillary pressure. As expected the influence of capillary pressure is more pronounced in buildup tests than in drawdown tests. A capillary pressure number is proposed to evaluate the importance of capillary forces over viscous forces in different regions in the reservoir.

For naturally fractured reservoirs, the effects of including capillary pressure in the fracture and matrix systems are investigated. It is observed that, under certain conditions, both drawdown and buildup tests show capillary pressure effects in different flow periods under transient conditions. Also, the influence of capillary pressure on the flow transfer between matrix and fracture is documented, observing that the oil flow rate per unit volume from the matrix to the fracture system is lower when capillary pressure is taken into account.

P. 421
An Instrumented Hydraulic Fracture Experiment in Coal
Authors: Jeffrey R.G. , Settari A.
Published: December 2007

A 28-meter thick composite coal mega seam, made up of coal and thin inter-seam tuff layers, was instrumented with piezometers installed in three monitoring wells around a central injection/production well. After characterization of the site by injection interference well testing and step-rate testing, two separate intervals in the mega seam were stimulated by hydraulic fracturing while the pressure response in the coal at the three monitoring wells was recorded. The minifrac and main treatment in the upper part of the mega seam produced a strong pressure response at one of the monitoring wells, allowing a calculation of fracture growth rate in the coal to be made directly from the observed response. The field fracturing data were supplemented by laboratory core testing, downhole video logging of the central borehole, and underground mapping of the hydraulic fracture geometry and coal structures when the coal mine workings advanced through the central well. The fracture treatment data, constrained by the mine back, propagation rate, and piezometer data, have been analyzed by numerical hydraulic fracture models to compare the model and observed pressure response and fracture geometry. One of the fracture models used is a design model intended for use in coalbed methane stimulation design and, as such, includes permeability and leakoff as a function of effective stress around the fracture and the effect of non-linear and non-elastic deformation of the coal on fracture width.

P. 43