bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Interpretation of Vertical Pressure Gradients Measured at Observation Wells in Developed Reservoirs
Authors: Stewart George , Ayestaran Luis 
Published: December 2007

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

Abstract
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

Abstract
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

Abstract
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.
Petroleum Resource Assessment of Wilderness Lands by the U.S. Geological Survey
Authors: Miller Betty M. 
Published: December 2007

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

ABSTRACT
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.
Hard Rock Drilling Problems Explained by Hard Rock Pressure Plots
Authors: Gill J. A. 
Published: December 2007

ABSTRACT
Hard rock drilling problems are frustrating.
Hard rock pore pressure interpretation is baffling.
Because of slow drilling in hard streaks and absence of kicks (in overpressured shale sections), it is generally assumed pore pressures are close to "normal" over long depth intervals.
Many hard rock drilling problems (Table 1) could not be logically explained, if this were the case.
Nothing could be further from the truth. Hard rocks are difficult to drill because of the extreme zig-zags from overpressured shales to sub-normally pressured sands and carbonates (Fig. 1).
It is impossible to drill anywhere near balanced in both situations, simultaneously. Hard rock drilling problems caused by underbalance or overbalance (or both) are a result (Table 1).
But, a better understanding of the presence and magnitude of these pressure shifts (Fig. 1) will help us minimize the worst extremes of imbalance and more intelligently strike an optimum compromise, realizing that mud density and, especially, mud chemistry can never completely solve these hard rock drilling problems.
Well log pressure plots in these erratic stratigraphies are so difficult to interpret that they often have been considered useless.
The example pore pressure plots shown here, including the Pressure Evaluation Profile (PEP) log – a side by side comparison of several different pressure sensitive responses (Figs. 5, 10) – help interpret and explain many of these problems in a simple, logical manner.
PDC Bits Find Applications in Oklahoma Drilling
Authors: Offenbacher L. A. , McDermaid J. D. , Patterson C. R. 
Published: December 2007

Abstract
Drilling in Oklahoma is difficult by any standards. PDC bits, with proven success drilling soft, homogenous formations common in the North Sea and U.S. Gulf Coast regions, have found some significant "spot" applications in Oklahoma. Applications qualified by bit design and application development over the past two (2) years include slim hole drilling in the deep Anadarko Basin, deviation control in Southern Oklahoma, drilling on mud motors, drilling in oil base mud, drilling cement, sidetracking, coring and some rotary drilling in larger hole sizes.
PDC bits are formation sensitive, and care must be taken in selecting where to run them in Oklahoma. Most of the successful runs have been in water base mud drilling hard shales and soft, unconsolidated sands and lime, although bit life is often extended in oil-base muds,
Summary of API Onshore Drilling Mud and Produced Water Environmental Studies
Authors: Moseley H. R. 
Published: December 2007

Abstract
The restoration/disposal of drilling mud pits and produced water impoundments is a continuously growing concern to the oil and gas exploration/production industry. To ensure proper restoration of of these sites, it is first necessary to determine the environmental effects of drilling muds and produced waters to soils, plants, and surface/ground water. The American Petroleum Institute (API) has sponsored four major studies investigating these impacts to these onshore drilling and production sites.
Optimize Bit Hydraulics for Minimum Cost Drilling
Authors: Doiron H. H. , Deane J. D. 
Published: December 2007

Abstract
In a previous paper, the authors derived a condition for optimum bit hydraulics considering increases in rate of penetration, fuel costs and pump maintenance costs with increased bit hydraulics. This paper is an extension of the previous work and demonstrates practical application of the new hydraulics optimization method. Previously unpublished full scale laboratory drilling data obtained by the authors and test results reported by other authors are presented to demonstrate the relationship of ROP to increased bit hydraulic horsepower. Effects of blanked nozzles and asymmetric nozzle configurations are also presented. Graphical relationships of fuel and pump maintenance cost increases, bit ROP increases and drilling cost variations with increasing standpipe pressure and bit hydraulic horsepower are presented. The optimum condition for bit hydraulics reveals that fuel costs to power mud pumps and pump maintenance costs should be a fixed percentage of total operating costs depending on bit ROP response to increased bit hydraulic horsepower. Recommendations for field application of the optimizing technique are presented.
Bottomhole Pressures Measured While Drilling
Authors: Ramsey M. S. , Robinson L. H. , Miller J. F. , Morrison M. E. 
Published: December 2007

Abstract
Recent in-situ measurements show that major discrepancies exist between accurately measured net bit pressure drop values and those predicted by previously accepted models and equations. The direction of the discrepancies is such that the measured values of net bit pressure drop are 20 per cent lower than those predicted by the existing models. Subsequent laboratory data obtained under rigorously monitored and controlled conditions support the field-taken downhole data. These data, as well as a possible explanation, are presented in this paper.
The Drilling Contract—A Reflection of Market Conditions
Authors: Warren Ted 
Published: December 2007

Abstract
The drilling contract will accurately reflect current market conditions but often at the expense of improperly matching the operator's objectives and the contractors incentives. During a period of rig oversupply, both operators and contractors must avoid using an inappropriate type of contract which may result in loss of drilling efficiency and financial inequities. This paper discusses the factors that should determine whether a well is drilled on daywork, footage or turnkey.
A Strategic Exploration Model
Authors: Warren J. E. 
Published: December 2007

ABSTRACT
Since an estimate of available petroleum resources, and the size distribution associated with them, is a fundamental requirement for the development of a viable exploration program, a theoretical model that simply represents the exploration process has been developed to facilitate the estimation of remaining reserves, the assessment of past exploration performance and the formulation of future exploration strategy. Several commonly employed models have been cited as special cases of this more generalized model and their shortcomings have been indicated. The practical use of this model has been demonstrated with field data and its extension to strategic decision making has been suggested via example; i.e., to obtain an allocation of effort that will achieve specific objectives re expenditures, reserves and risk.
Simulation of a Major Oilfield Gas-Gathering Pipeline System
Authors: Brill James P. , Sifferman Thomas R. , Samaroo Brian , Arirachakaran Srihasak 
Published: December 2007

ABSTRACT
Diameters from 30 to 40 in. (76. 2 to 101.6 cm) were evaluated for two pipelines planned for a gas gathering system in a major offshore oilfield in Saudi Arabia. The dew point gas from separators will undergo retrograde condensation in the pipelines with reduction of pressure and temperature. Calculations required for sizing the pipelines include phase behavior, pressure drop, temperature profiles liquid volumes, flow pattern predictions, liquid flow rates and the minimum gas velocity required to continuously remove liquid from the risers.