bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical Simulation of In-situ Combustion of Sensitive Heavy Oil Reservoir
Authors: Wenlong Guan , Shuhong Wu , Shihu Wang , Junhe Cao , Yaping Chen
Published: December 2007

Block Z, one of reservoir of Shengli Oil Field, is a sensitive heavy oil reservoir with high content of kaolinite and illite. From 1992 to 2002, more than ten-year's water drive and steam huff and puff had seen poor production performance. In 2003, in-situ combustion pilot test with 1 injector and 11 producers was carried out to improve development performance and, simultaneously physical simulation is designed to evaluate the pilot test. The paper will detail the physical experiments of in-situ combustion, its experiment apparatus, its process, and its results. Also, it will briefly introduce production history and performance of pilot test.

Several experiments have been carried out and the results show that air injection rate is the key factor to influence the fire flooding, the higher injecting rate and the higher the advancing speed of combustion front. For complete combustion with plentiful air supply, no coke comes into being and the formation remains undamaged without permeability decrease. For the sensitive reservoir, the component of rock has changed after burning, and the reservoir has turned into low sensitive to water and steam. In front of burning zone, high oil saturation bank is formed, in which pressure decreases greatly during fire flooding. When the bank is away from the producer, the producer shows low productivity. Once it goes near to the producer, productivity increases step by step.

Experiment results have been successfully used to evaluate the pilot test and to improve the performance. Up to now, the pilot test has been lasting for more than 3 years and more than 26.7×103t oil has been produced.
Case History—Installation of High Volume Pumping Equipment in Talco Field, Texas
Authors: Rose James D.
Published: December 2007

The paper presents a case history study of Exxon's high volume artificial lift program at Talco Field in Franklin and Titus Counties, Texas. The field, discovered in 1936, produces heavy crude oil from the Paluxy Sandstone at an approximate depth of 4200 feet. All wells required artificial lift installation soon after the field was discovered due to rapid salt water breakthrough. Primary recovery efficiency is expected to be only about 35 percent of the original oil in place, attributed to reservoir heterogeneity and the adverse water-oil mobility ratio. Through installation of high volume artificial lift equipment, current data indicate that significant additional recovery benefits may be realized.

The paper details the practical experience Exxon has gained since the first high volume electric submersible pump was installed at Talco in 1974. Included are screening parameters used to optimize the selection of particular high volume artificial lift equipment. Also included are representative production flowstreams to quantify the additional recovery expected of typical electric submersible pump and large capacity beam pumping unit installations. An analysis of the incremental expenses and costs associated with electric submersible pumps and large capacity beam pumping units is presented. Also discussed are case production histories and operational problems encountered with actual installations.
Optimisation of Solids Control Opens Up Opportunities for Drilling of Depleted Reservoirs
Authors: Omland T. H. , Dahl B. , Saasen A. , Taugbøl K. , Amundsen P. A.
Published: December 2007

Experience has shown that adding suitable particles to the drilling fluid can significantly improve the formation strength. This is especially beneficial when drilling wells with a narrow operational window as is typically the case when drilling depleted reservoirs. Successful operations have employed several types of particles, including graphite and calcium carbonate. For this kind of approach to work, it is important to establish an optimal particle composition in the drilling fluid. In a recent paper, SPE 107574, the possibility for continuous monitoring of the particle size distribution (PSD) and particle content in the drilling fluid, was demonstrated. This present work shows how these findings have allowed deploying a unique technique for running of solids control equipment in a North Sea offshore field, providing optimal particle concentration and size distribution when drilling a significantly depleted reservoir. We describe in detail an HTHP offshore operation where coarse shaker screens were used to allow relatively large particles to re-enter the well during circulation. These particles act just like particles deliberately added to the drilling fluid in order to enhance formation strength. The monitoring equipment allowed for close control of the PSD of the drilling fluid flowing into and out of the well during drilling. The particle size distribution is compared to that obtained with conventional additives previously used to achieve formation strength enhancement.
Silurian-Niagaran Reef Belt Around the Michigan Basin—A Synergistic Review
Authors: Aminian Khashayar , Tek M. Rasin , Wilson James L.
Published: December 2007

The Silurian-Niagaran pinnacle reefs occur on a belt which encircles the entire Michigan Basin including areas presently covered by the Great Lakes. The annual production from these reefs in Michigan has reached 30 million barrels of oil and 150 billion cubic feet of natural gas.

Two different structural settings existed in the Michigan Basin during the Silurian Period, which resulted in formation of the pinnacle reefs with somewhat different characteristics in different parts of the basin. The pinnacles of the northern trend occur at depths of 4000-7000 feet, are up to 700 feet thick, and average about 100 acres in area. The southern pinnacles occur at depths of 2000–3000 f shorter, about 300 feet thick, and attain larger areas. The pinnacle reefs underwent several diagenetic changes, which resulted in concentration of the majority of the hydrocarbon reserves of the northern trend in pinnacles which occur on a band 3-4 miles wide inside the middle of the trend. There exists a regional partitioning of oil and gas in the northern pinnacle reefs, which can best be explained by Gussow Theory of migration and differential entrapment. Such a reserve concentration or hydrocarbon differentiation has not been observed in the southern trend.

A probabilistic model for exploration in a play was found applicable in mature areas of the northern trend and the results were extended to other parts. The results suggest that the effectiveness of exploration, based on seismic surveys, is 8 to 10 times better than random drilling. The reserves of the reef belt are in excess of 7 billion barrels of oil and 15 trillion cubic feet of natural gas in place.
Simulation of the Wellbore Hydraulics While Drilling, Including the Effects of Fluid Influxes and Losses and Pipe Washouts
Authors: Millheim Keith K. , Tulga Said Sahin
Published: December 2007

This paper presents a method to simulate the circulating system while drilling a well. For any given pump rate the pressure losses through the surface system, down the drill pipe, through the bit, and up the annulus can be determined. The algorithm also has the capability of simulating a washout in the drill string, losing fluid to the formation, having fluid produced into the annulus, and fracturing the formation(s).

The algorithm is general enough to calculate pressure losses for turbulent and laminar flow, simultaneously. This covers the situation where multiple flow regimes exist in the same circulation loop.

Formulation of the algorithm is presented, showing how a network type of solution is used to calculate the pressures and flows. The iterative solution converges rapidly and can be used for real time and faster than real time simulation.

Detailed surface pressure data was obtained from two wells in Texas. The circulation simulation program was used to calculate pressure losses at various depths in each well for a variety of circulation rates. Results presented in this paper show close agreement with the field data.

To show the versatility of the simulation algorithm a series of idealized circulation system simulations are presented. These include various downhole circulation situations such as lost circulation, circulation without returns, and fluid production response as a function of permeability and pressure, and circulating with a hole in the drill string.
Flow Enhancement Characterizes Design of Polycrystalline Diamond Cutter Bits
Authors: Kuhn Karl O. , Forrest Scott
Published: December 2007

The design and development of a drag bit that utilizes polycrystalline diamond drill blanks requires careful attention to hydraulic design features. For optimum performance and service life, the polycrystalline diamond drill blanks must be kept cool and clean. These critical hydraulic requirements, vital to the survival of the diamond drill blanks, were resolved by optimizing flow velocities across the cutters as well as with the proper distribution of flow volume. This was accomplished with strategically located flow re-strictors and the incorporation of numerous interchangeable carbide jet nozzles.

Field test results of polycrystalline diamond cutter bit runs in Louisiana and Texas show that significant savings can be realized by using these bits in specific drilling situations.
Evaluation of the Gas Production Potential of Marine Hydrate Deposits in the Ulleung Basin of the Korean East Sea
Authors: Moridis George J. , Reagan Matthew T. , Kim Se-Joon , Seol Yongkoo , Zhang Keni
Published: December 2007

Although significant hydrate deposits are known to exist in the Ulleung Basin of the Korean East Sea, their survey and evaluation as a possible energy resource has not yet been completed. However, it is possible to develop preliminary estimates of their production potential based on the limited data that are currently available. These include the elevation and thickness of the Hydrate-Bearing Layer (HBL), the water depth, and the water temperature at the sea floor. Based on this information, we developed estimates of the local geothermal gradient that bracket its true value. Reasonable estimates of the initial pressure distribution in the HBL can be obtained because it follows closely the hydrostatic. Other critical information needs include the hydrate saturation, and the intrinsic permeabilities of the system formations. These are treated as variables, and sensitivity analysis provides an estimate of their effect on production.

Based on the geology of similar deposits, it is unlikely that Ulleung Basin accumulations belong to Class 1 (involving a HBL underlain by a mobile gas zone). If Class 4 (disperse, low saturation accumulations) deposits are involved, they are not likely to have production potential. The most likely scenarios include Class 2 (HBL underlain by a zone of mobile water) or Class 3 (involving only an HBL) accumulations.

Assuming nearly impermeable confining boundaries, this numerical study indicates that large production rates (several MMSCFD) are attainable from both Class 2 and Class 3 deposits using conventional technology. The sensitivity analysis demonstrates the dependence of production on the well design, the production rate, the intrinsic permeability of the HBL, the initial pressure, temperature and hydrate saturation, as well as on the thickness of the water zone (Class 2). The study also demonstrates that the presence of confining boundaries is indispensable for the commercially viable production of gas from these deposits.
Interwell Pressure Testing for Field Pilots
Authors: Stegemeier George L.
Published: December 2007

Procedures are described, and results are compared with core analyses, for a number of transient pressure experiments that were carried out between wells in a small chemical flood pilot. Tests include: (1) a standard pulse test, (2) a simultaneous pressure buildup and falloff of wells in a five-spot pattern, (3) a reverse pulse test, in which response from a producer was measured at a nearby injector during injection, and (4) production drawdown tests from normally shut-in observation wells during polymer injection and during subsequent waterflood in a nearby injector. Flowing these observation wells provided an effective way to measure in-situ mobilities of injected fluids.

For pulse tests, a simplified method for design and interpretation of single pulses is derived from basic equations. Dimensionless functions, representing directional permeability and geometrical mean permeability, are shown to be functions of a single dimensionless time lag of the maximum pressure response. For large dimensionless time lags, the ratio of dimensionless permeabilities approaches the value πe and simple geometric relationships may be used to predict either compressibility or formation thickness.
Case Histories: New Perforating Technology Enhances Workover Operations in Difficult Scenarios
Authors: Bargawi Riyadh A. , Dean Doyle , Clemens Jack , Dove Johnny
Published: December 2007

Wells in Saudi Arabia, onshore and offshore, often require workover because of the highly corrosive environment to which the downhole equipment is subjected. During these operations, the downhole equipment often must be repaired or replaced. To maintain well control during these workovers, a single hole often is required to allow the kill fluids to be circulated. Traditionally, these holes have had to be made with explosives and a "Soft Shot" perforator or by mechanical hole-punching methods. Workover jobs that required a single hole to be punched were often economically compromised by the delays in mobilizing explosives and because failures to perforate "soft" tubing were common when using traditional mechanical hole-punching methods.

This paper presents several case histories in which a newly developed slickline-deployed, electro-mechanical tubing punch was used for the first time worldwide. Although the workover requirements in the wells differed and were in both onshore and offshore environments, all required a single hole to be punched. The method was 100% successful and solved the problems that had been experienced using conventional methods.
Horizontal and Multilateral Drilling Technology: Contribution Towards Production Improvements of Naturally Fractured Reservoir (Case Study, Algeria)
Authors: Benzagouta Mohammed S. , Amro Mohammed M.
Published: December 2007

The studied oilfield is located in Algeria. The reservoir succession is subdivided in four lithological parts. Two main parts form the special focus of this study: part 1 and part 2. Results, based on permeability and porosity, show very low values, close to the standard cut off. The presence of fractures with a high frequency may have an important impact on production. These fractures have been identified by the use of the borehole image tools. These fractures are of different types: opened fractures and half opened and sealed. In their pattern, these fractures are longitudinal and transversal. Contribution of fractures towards the change in permeability and porosity shows a variable fluctuation, despite their considerable frequency. Thus and owing to the reservoir characteristics and their evolution, gathered to the fracture aspect presence and, for better efficiency, requirement for an application of advanced drilling technology is ideal. Therefore, the horizontal drilling type may remain an ultimate option. Since the target is to intersect a high number of fractures. The length of the horizontal section might not be long, and therefore high DLS might be tolerated. Productivity from horizontal wellbore can be as much as 20 times greater than from a comparable vertical well. The major reason for such improvement is that a horizontal wellbore affords much greater exposure to the producing zone. However, the drilling cost of a horizontal well will not exceed 2 to 2-1/2 times that of a vertical well. The advantage of horizontal drilling in such area will be also debated.
Intelligent Completions Technology Offers Solutions to Optimize Production and Improve Recovery in Quad–Lateral Wells in a Mature Field
Authors: Abduldayem Mohammed A , Shafiq Muhammad , Al Douhan Nader D. , Baluch Zulfiqar A.
Published: December 2007

This paper describes an innovative completion solution with state-of-the-art reservoir monitoring and control completion technologies that allows commingled oil production from quad laterals wells in Abqaiq field. Many intelligent completions wells have been successfully installed in Abqaiq, operated by Saudi Aramco. Included in the description are equipment selection, design and development details, installation procedures, and "lessons learned" after installation of the fully hydraulic tubing-retrievable advanced completion system with digital permanent down hole monitoring system.

Intelligent completions will allow individual lateral testing and allocation of production rates to optimize each lateral contribution and the overall commingled well rate. Along with real time monitoring, sustainability of well rate will be extended by timely reacting to any changes to reservoir and well conditions.

Using variable-position flow control valves, early water breakthrough can be delayed, to increase recovery. Monitoring the flowing pressure in real time allows producing the well at optimum rate; i.e., above bubble point pressure. Ultimately, intelligent completions will limit the water handling at the surface and concurrently increase the recovery factor in heterogeneous fractured and fissured carbonate reservoirs for MRC (Maximum Reservoir Contact) wells.
Integration of NMR with Other Open Hole Logs for Improved Porosity, Permeability and Capillary Pressure of Gas Sand Reservoirs
Authors: Hamada G. M. , Oraby M. El. , Abushanab M. A.
Published: December 2007

Analysis of tight gas sand reservoirs is one of the most difficult problems. Many tight formations are extremely complex, producing from multiple layers with different permeability that is often enhanced by natural fracturing. Therefore, looking for using new well logging techniques like NMR in individual bases or in combination with conventional open hole logs and building new interpretation methodology is essential to well define and obtain the representative reservoir characterizations.

Nuclear magnetic resonance (NMR) logs differ from conventional neutron, density, sonic and resistivity logs because the NMR measurements provide mainly lithology independent detailed porosity and a good evaluation hydrocarbon potential. NMR logs can be used to determine formation permeability and capillary pressure.

This paper concentrates on three petrophysical applications of NMR; 1) present a technical method for porosity calculation in which density and NMR porosities are combined and calibrated to core, 2) Use new empirical method of bulk gas volume (BG) in the invaded zone for permeability estimation termed BGMRK and 3) Use T2 distribution for capillary pressure approximation and correct pore size distribution for gas.

These applications of NMR logs have been applied in a gas sand reservoir field of different facies and permeability varies from less than 0.1 md to more than 100md related to facies changes. These applications result in a) The technique of using combined NMR and bulk density data significantly reduces uncertainty in porosity through elimination of the neutron log down to 0.5%. b) The new approach of "BGMRK" resulted in very simple facies independent model to calculate reliable permeability 2. c) Capillary pressure can be approximated from NMR T2 distribution and then the integration between cap-curves and T2 distribution can be corrected for partial pores fluid fill.
Reduced Water Production and Increased Oil Production Using Smart Completions and MPFM "Case Study"
Authors: Al-Shenqiti Mohammad S. , Dashash Alaa A. , Al-Arnaout Ibrahim H. , Al-Driweesh Saad M. , Bakhteyar Zaki
Published: December 2007

Saudi Aramco's drilling strategy witnessed a change in the last few years by drilling horizontal and extended reach maximum reservoir contact (MRC) wells. One of the objectives behind this strategy is to improve the well productivity by maximizing oil production and minimizing water production. The paper will demonstrate the challenges and successes of reducing produced water by using smart completions and how multiphase flow meters (MPFM) helped in getting better results to allow faster decision making. In one of the challenging areas in Ghawar field where the water will reach the wellbore much faster via the reservoir's fractures. Using the smart completion with the conventional rate testing (the plant's testing facility) required longer time to reach the best possible setting for the downhole flow control valves to achieve the optimum flow rate. Using the combination of smart completion and portable MPFM (Multiphase Flow Meter), resulted in reducing the water cut (WC) form 20% to 0% maintaining the same required average oil rate (Fig. 1), and enabled better reservoir management. The results from this experience, as will as other experiences, have been utilized in a recent major increment in the Ghawar field that was mainly developed using multilateral MRC wells equipped with downhole smart completions and surface MPFMs.
Log-Based Geomechanical Characterization and Sanding Potential Analysis on Several Wells Drilled in Southern Part of Oman
Authors: Franquet Javier A. , Stewart Gregory , Bolle Luc , Ong Seehong
Published: December 2007

This paper presents a methodology to analyze sanding potential on clasticreservoirs by determining the critical drawdown pressure required to on-setsand production. The critical drawdown pressures are obtained from ananalytical model that describes the mechanical stability of a perforationcavity in a Mohr-Coulomb material under Darcy flow regime. The study wasperformed on several wells from different oil fields in South Oman with themain objective to identify the formation intervals with the greatest sandingpotential.

The critical drawdown assessment requires geomechanical characterization ofthe formations of interest. Static mechanical properties and strengths wereobtained from a log-based program. This program is based on FORMEL; which is aconstitutive model describing the microscopic processes occurring in a rocksample during triaxial loading. The basic inputs for running the model are welllog information, petrophysical volumes, and the pore fluid properties of theformation. The geomechanical characterization and the pore pressure profilewere used to calculate the maximum drawdown pressure needed before sandingoccurs on foot by foot basics. A clear correlation was found between lowstrength formations and the intervals with low critical drawdown pressurevalues.

The analysis allows identification of high sanding potential intervals for aselective perforation program, and it supports gravel pack decisions whererequired. Also, the critical drawdown profiles assist to choose a suitable sandcontrol completion technique, ranging from classic gravel packing tostate-of-the-art expandable sand screen installations.

Introduction

Knowledge of rock mechanical properties is important for the planning of bothdrilling and production strategies. Traditionally, rock mechanical propertiesare obtained directly from laboratory triaxial tests on core samples. Hence, mechanical properties are typically only defined at discrete depths were thecore samples were taken and lab values can be skewed due to the core handlingprocess. Accurate sand production prediction, however, requires a continuouspresentation of mechanical properties with depth including the cohesivestrength and internal friction angle of the rock.
Successful Water Shut Off Treatment With Engineered Micro-Cement Slurry Through Coiled Tubing in Pakistan
Authors: Jamil Ainul H. Abdul , Ahmad Tofeeq
Published: December 2007

This paper describes the success story of the first water shut off treatment using Engineered Micro-cement Slurry (EMS) through Coiled Tubing in Pakistan. The well was an oil well producing from multiple zones, but mainly the lower zone (C-Sand). Due to high water cut, it was decided to isolate the C-Sand and to produce only from the upper perforations (A/B Sands). Based on economics and technical feasibility, water shut off treatment through a cement plug was selected to isolate the C-Sand zone. 148ft of cement plug was squeezed and spotted across the C-Sand through coiled tubing using conventional cement slurry. After setting the cement plug, water cut was reduced by 23% and the well initially produced up to 380bopd from the A/B Sand. After 3 months production, water cut level increased drastically back to 100%. A slickline run confirmed that the cement plug had failed and top of cement dropped 48ft from its original depth. It was suspected that the plug failed due to possible contamination in the cement, which enabled water to channel up across the plug. A remedial cement plug through coiled tubing was subsequently set, but this time using EMS slurry to ensure that any channels in the previous plug were cemented and ensuring that the perforations were sealed off completely. The job was conducted successfully and the water cut was reduced by 25%, with initial production of 500bopd from the A/B Sands.
Subsurface Fracture Analysis in Carbonate Reservoirs: Kohat/Potwar Plateau, North Pakistan
Authors: Jadoon Ishtiaq A. K. , Bhatti Khalid M. , Siddiqui Fareed I. , Jadoon Saeed K. , Gilani Syed R. H. , Afzal Munazzah
Published: December 2007

Carbonate reservoirs in Northern Pakistan are characterized by tight limestone. In these reservoirs, fractures are important for production and reservoir modeling. This paper addresses problems related to subsurface fracture analysis based mainly on image logs.

Natural fractures occur as systematic and unsystematic sets of definite and random orientation respectively. The subsurface analysis of fractures uses electrical and acoustic image logs to characterize fractures as either natural or induced features. They are classified as conductive or resistive features, representing possibly open or closed (mineralized) fractures, respectively. Using image logs, natural fractures are interpreted and classified descriptively to be continuous or discontinuous features representing systematic fractures or classified as chicken-wire (microfractures) fractures representing unsystematic sets. Statistical analysis of fractures is used to classify them into geometrical and genetic sets as longitudinal (extensional), transverse (tensional), and oblique (shear) to the structure. Transverse fractures are known generally as most open. They develop parallel to the maximum horizontal in-situ stress and extend deep into the structure. Longitudinal fractures, those parallel to the fold axes, are observed to produce hydrocarbons in several fields in Northern Pakistan. Fracture density impacts production and reserves calculations. However, fracture density is strongly influenced by the lithology and layer thickness. Widely spaced fractures are observed in massive carbonate reservoirs, and closely spaced fractures of narrower aperture are observed in laminated strata. Thus, individual fractures in massive carbonates require to be identified for their impact on production. Fractures are observed to occur as discontinuous features of right or left-stepping geometry and as en echelon features of significantly wider aperture in shear bands. These features together with vugs and leached features may provide zones of higher porosity, permeability, and storage capacity with isolated distribution in tight carbonates. Therefore, knowledge about fracture occurrence and distribution is important to predict sweet spots for drilling and field development.
Saudi Arabia's Master Gas System—Its Overview and the Corrosion Control Programs
Authors: Chen Edmund Y. , Al-Helal Fahad Eid
Published: December 2007

This paper presents an overview of Saudi Arabia's Master Gas System (MGS), specifically the Phase I program. All the source gases, collected from the various fields, are associated with sour crude production. Significant potential corrosion problems arise in the handling and processing of these gases. For this reason, extensive corrosion control programs have been implemented in the very early stage of the program. In this paper, the related corrosion control measures will be discussed. Some facilities in the MGS have been in operation for more than two years. Corrosion monitoring data indicates that corrosion has been under good control.
A Laboratory Technique for Screening Shale Swelling Inhibitors
Authors: Roehl Edwin A. , Hackett James L.
Published: December 2007

A new technique was developed for quantitatively analyzing the effectiveness of shale swelling inhibitors in retarding fluid adsorption and volume expansion. Details of testing procedures, equipment construction, and design rationale are provided. Comparisons are made to methods commonly used in mud labs today, and examples of test results are given to illustrate the new technique's usefulness and versatility. Relevant concepts of clay hydration theory are discussed to provide background for interpreting the presented experimental results. Differentiation between crystalline swelling, and combined crystalline and osmotic swelling is achieved by applying a mechanical restraining force (preload) to shale samples while being hydrated. Mud additives examined include various salts, ferrochrome lignosulfonate, and several polymers.
Stochastic Modeling of Two-Phase Flow in Porous Media
Authors: Smith Peter J. , Brown Christopher E.
Published: December 2007

A recurring problem in Reservoir Engineering is how the innate variability of geophysical systems can be appropriately modelled. In recently published studies variability has been introduced into the models of single phase flow by expressing them as stochastic processes. Following this development the aim of this paper is to establish the main characteristics of immiscible flow in a non-uniform porous medium represented as a stochastic process. For this purpose Monte Carlo simulation is appropriate. Both steady-state and transient (ie. displacement) systems are examined. Differences in the one and two dimensional simulation behaviour emphasise the importance of correct averaging to produce representative parameters. Direct results of this study are to the use of composite heterogeneous cores. In the longer term a basis is established for the development of reservoir engineering models formulated in a stochastic form.
The Interpretation of Vertical Pressure Gradients Measured at Observation Wells in Developed Reservoirs
Authors: Stewart George , Ayestaran Luis
Published: December 2007

When distributed pressure measurements are made with an RFT survey in a new well in a developed reservoir in many cases a near linear pressure-depth relation is observed. In some zones vertical pressure equilibrium is evident while in others the measured profile does not correspond to the hydrostatic gradient of the in-situ fluid because of viscous effects associated with a vertical flow component. The direct demonstration of the existence of, or deviation from, vertical pressure equilibrium gives valuable information on reservoir behaviour. The use of pressure gradient data in reservoir zonation and performance analysis through mathematical models is considered. Simplified models of differential depletion show how vertical flows in the reservoir may be inferred from production logging measurements in the wells. With this information the observed pressure profiles may be interpreted for the effective vertical permeability of barriers and tight zones. In the case where the well penetrates a zone containing two mobile fluids the theory of countercurrent gravity segregation is used to show how the measured gradient can correspond to the hydrostatic gradient of either fluid depending on the mobility ratio, or to an intermediate case. The difference between vertical pressure equilibrium in single-phase flow and vertical saturation equilibrium in two-phase flow is discussed.

In low permeability zones the pressure measured by a probe at the sandface can be affected by mud filtrate invasion and the pressure observations deviate from undisturbed formation pressures. Analysis of the invasion process shows how the sand-face pressure is related to the true formation pressure and the mud fluid loss rate and the local permeability are the controlling factors. The successful testing of tight zones depends on being able to set the probe in locations of sufficiently high permeability for invasion effects to be small. Permeability estimates from the buildup associated with each pressure test are used as a quality control parameter for the pressure measurements. The stochastic nature of the pressure observations is demonstrated and the minimum interval over which a pressure gradient can be determined within a given error bound is considered.
Pressure Transient Testing With A Partially Penetrating Well In A Two-Layer Reservoir
Authors: Javandel Iraj , Witherspoon P. A.
Published: December 2007

Estimating flow properties of a heterogeneous reservoir consisting of two or more layers with different flow properties is often a problem of great interest to reservoir engineers. Analysis of pressure transient data from a partially penetrating well producing from either layer of a two-layer reservoir may be used to estimate the individual transmissivities.

An analytic solution has been derived to investigate the transient pressure response of two-layer reservoirs with cross-flow. Results of the analytic method have been verified using a finite-element model and they reveal important details of pressure transient behavior such as the limiting conditions for detecting a multilayer situation. A procedure has been developed to evaluate the permeability of the producing layer as well as that of the second layer. The method can be applied to both pressure buildup and interference well tests. As has been previously shown from earlier numerical techniques, the early-time response of such a two-layer reservoir producing from a fraction of the thickness of one or the layers closely follows the behavior of a single-layer case. An inflection point in the pressure response can be expected under certain circumstances, and this provides important data. At large times the system behaves like an equivalent homogeneous reservoir.
MWD Field Use and Results in the Gulf of Mexico
Authors: Roberts Andrew , Newton Robert , Stone Frederick
Published: December 2007

Measurement-While-Drilling (MWD) is an important new technology for transmitting data from the bottom of a borehole to the surface without a wireline. The biggest application now is for directional drilling where MWD virtually eliminates downtime for directional surveys.

The Teleco MWD system is the first to be used extensively in the Gulf of Mexico. In this paper we discuss our field experience in the Gulf of Mexico and the methods and standards that evolved with the introduction of this new technology. We also present an analysis of direct time savings based on data from 31 MWD-surveyed and 31 conventionally-surveyed wells and we use case examples to illustrate other benefits of the MWD system.
Dynamics of Moving Interfaces in Porous Media: I. Instantaneous Velocity Field
Authors: Kale Dilip M.
Published: December 2007

Mobility changes from region to region can occur in a reservoir due to inhomogeneities in permeability and due to change in saturating fluid. In either case interfaces are present across which mobility changes abruptly. The problem of fluid flow in porous media in the presence of such interfaces is solved in this paper by using complex velocity potentials.

On the interface tangential component of efflux vector is discontinuous. A vortex sheet appears on the interface and it affects the flow. Complex velocity potential in such a case can be expressed as a linear superposition of the potentials due to sources (injection wells), sinks (production wells) and due to vortex sheets along the interfaces of mobility discontinuity. Vorticity distribution on interfaces and the velocity field are inter-related. Therefore we get an integral equation for the vorticity distribution. The solution of the integral equation enables us to define the complex velocity potential completely and hence the velocity field in the flow region.

It is shown that in the general case of several wells and interfaces the integral equation has a unique solution and leads to a unique flow pattern. An exact solution of the integral equation for a circular interface is obtained. An impervious no-flow boundary is an extreme case of mobility discontinuity. It is shown that its effect on the flow can be considered by an appropriate vortex sheet along it. Thus a formal solution in the form of an integral equation is obtained for instantaneous velocity distribution for arbitrary well pattern and mobility distribution.
Energy Financing in Times of Uncertainty
Authors: David Amiel , Carson G. P.
Published: December 2007

After a decade of increasing prices, conditions in the domestic petroleum industry changed adversely for many companies in 1982. Perceptions of the future value of reserves by the financial community have an impact on the ability of producing companies to borrow against those reserves.

This paper will discuss how a group of oil and gas banks determine loan value using an identical reserve base. Also examined is the difference in loan value a particular bank will arrive at in todays environment versus the loan value that would have been reached at the beginning of 1982.

The variables used in determining a loan amount are analyzed, and their sensitivity to different scenarios are examined. Pricing forecasts, the split of value between oil and gas, the discount rate, and the loan coverage ratio for different banks are compared. The conclusions illustrate the importance of loan coverage and the most sensitive areas to consider in keeping loan to collateral margins satisfactory.

The methods banks use to determine the amount they are willing to lend will vary with each bank's experience in energy lending, the size and skill of its engineering staff, and to a some degree its emphasis on energy lending. A survey taken among energy lenders indicates the loan amount tends to be similar despite the variety of methods used.
How Deregulation of Natural Gas Will Affect Design of Gas Production and Processing Facilities
Authors: Hubbard R. A.
Published: December 2007

Natural gas prices have been partially or totally controlled at the wellhead since 1954.1 While regulation has created problems for natural gas producers, it has spurred the development of the most extensive and sophisticated natural gas processing industry in the world. The 1.5 MMBPD of gas plant NGL production in the United States is a vital part of the economy. Under current law, in 1985 it is estimated that approximately 50%-60% of the natural gas production in the United States will be deregulated. In 1987 an additional 5%-10% will be deregulated.2 Deregulation removes the guaranteed ceiling cost of fuel and shrinkage for gas processors. This paper assesses the effect of deregulation on the gas processing industry, and discusses how the industry may change after deregulation.
Economics for Nonassociated Gas Production by Field Size, Depth, and Region
Authors: Wood J. H.
Published: December 2007

This paper presents the relative economics to develop and produce non-associated gas from nine field sizes at four depths in eight U.S. regions. Exploration costs are excluded. In general, for a given field size it requires roughly twice the price to yield the same discounted cash flow rate of return as depth increases from 7,500 to 12,500 feet. The price roughly doubles again in going from 12,500 feet to 17,500 feet. At each depth, a large increase in price was required for economic development as field size decreases. Regional factors can also have a significant bearing on field economics especially where drilling and operating costs are exceptionally high.
A Mathematical Model for Budgeting Exploration Efforts
Authors: Freeman F. V.
Published: December 2007

On the company executive level, the need exists for a forecasting approach less sensitive to individual exploration prospects and more sensitive to overall performance. To answer this need, a mathematical model for exploration efforts has been developed. This model calculates results required to obtain certain economic performance levels.
Petroleum Resource Assessment of Wilderness Lands by the U.S. Geological Survey
Authors: Miller Betty M.
Published: December 2007

The U.S. Geological Survey is conducting an investigation of the oil and gas resource potential of the existing and proposed Wilderness Lands in the western United States. This paper discusses the procedures used to combine a variety of geologic and geographic data, along with logged information on wells and petroleum statistics, by applying computer and αigital cartographic techniques for the purpose of assessing the petroleum resources in the Wilderness Lands, The methodology briefly described in this paper involves a review by geologists of existing information and evaluating the geologic characteristics for each Wilderness tract to determine the favorability, or lack of favorability, for petroleum occurrence. The assessments of the petroleum resources are reported in two phases: by a designated qualitative rating of the petroleum potential for each Wilderness area, displayed on state maps; and by estimating the fractional amount of the oil and gas within each province or basin that occurs in the Wilderness Lands, expressed as probability distributions for the quantitative estimates. This is a progress report of the U.S. Geological Survey's work to date on the assessment of the petroleum potential of the western Wilderness Lands.
Boom or Bust: Charting the Consequences of Governmental Regulations
Authors: McClure G. J.
Published: December 2007

The purpose of this paper will be to chart historical financial performance of oil and gas against a backdrop of legislative events. To that end, the paper will have three distinct sections.

First, each of the major pieces of legislation that have had significant impact on the petroleum industry since 1975 will be presented. In this section, the discussion will be focused on the historical basis and subsequent evolution of each bill.

Second, a comparison will be drawn to illustrate the effects each major piece of legislation had upon net profits to the industry. Changes that were occurting as various statutes took effect will be demonstrated by an examination of some of the financial indicators of a typical project in oil and gas. Where applicable, a specific profile of the independent producer will be addressed.

In the third section, the paper will move into an analysis of proposed legislation. Specifically, the goal will be to address bills as they are currently drafted and provide a discussion of their potential consequences to petroleum economics. The decontrol of natural gas is one such issue which will merit special attention.
Mathematical Description of Detergent Flooding in Oil Reservoirs
Authors: Fayers F.J. , Perrine R.L.
Published: December 2007

This paper presents a mathematical description of detergent flooding of oil reservoirs. With several assumptions, this description reduces to a hyperbolic system of partial differential equations. The method of characteristics proves to be a suitable method of solution, particularly because multiple shock behavior is inherent in the system.

Introduction

For many years the problem of increasing ultimate recovery of oil from a reservoir has been a subject of interest to the oil industry. At present, a standard secondary recovery technique is to flood the reservoir with water when natural forces of the system are depleted. The permeability characteristics of the rock, together with interfacial forces which exist between the two fluids and porous material, allow only part of the oil in the rock formation to be recovered by water flooding. Laboratory experiments have shown that when detergents are added to the flooding water, flow properties of oil in a porous rock are improved. This improvement results in greater oil recovery. Even though higher recoveries are obtained using detergents, extra cost associated with the method may make it economically unsatisfactory. To establish economic feasibility requires either extensive field trials, or laboratory tests together with a calculation method describing field behavior. Pilot tests with field systems take years to complete; then the results must be interpreted. The interpretation is often no more certain than predictions based on laboratory data. For these reasons we have developed the mathematical representation of detergent flooding discussed here. The mathematical solution can be used with laboratory tests for detergent flood evaluation.
Future Semi-Submersible Drilling Units
Authors: Hammett D. S.
Published: December 2007

The petroleum industry, over the past 20 years, has increased its capability to drill in rough ocean environments by developing the semi-submersible type hull form drilling vessel. This paper presents the past history, present achievements, and predicts the future of the semi-submersible hull form.

The petroleum industry is experienced in using the column-stabilized semi-submersible (SSM) to drill and survive severe ocean storms in which other marine vessels either go to sheltered water or run from the storm. Two recent major accidents, the OCEAN RANGER and the ALEXANDER KIELLAND, involving the SSM hull form have resulted in a re-examination of inspection and regulation requirements. This paper describes some of the actions that designers, operators, classification societies and the petroleum industry are taking to insure that accidents like these two do not occur again. The impact of these accidents on worldwide usage of existing and future SSMs is also discussed.

The conclusion of this paper outlines design modifications which are required for safe worldwide use of the SSM and includes topics such as structural redundancy, reserve buoyancy, secondary ballast and lifesaving facilities.
Suitability of High-Speed Engines in Drilling Industry
Authors: Dugan R. W.
Published: December 2007

Diesel engines have wide acceptance as power sources by the drilling industry. Many factors are considered when selecting a primary power source, but the diesel's reputation for high reliability and durability is generally a major reason for the selection of diesel power.

A simplistic definition for reliability is:

Reliability is a measure of how well the engine was built.
Exploration Drilling in the Alaskan Beaufort Sea
Authors: Dragnich R. G.
Published: December 2007

Exploration drilling in the arctic presents many unique problems, which are largely logistical in nature. This paper discusses Exxon's operations and specific approaches used to solve these problems. The paper is limited to surface considerations. It is intended to give the reader an appreciation of operating in the arctic and to provide insight into the planning requirements.