bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Closed-Chamber Theory to Backsurge Completion Testing
Authors: Simmons J. F. , Grader A. S.
Published: December 2007

This paper presents a transient-pressure analysis method for the closed-chamber oilwell test. This method allows determination of reservoir transmissivity and wellbore skin with log-log type-curve matching. The method is believed to be applicable to analysis of perforation-cleaning backsurge data. A solution is obtained by superposition of the cumulative-influx, constant-pressure solution of the radial diffusivity equation. Superposition avoids many of the limitations of direct solution and facilitates consideration of nonideal chamber gas behavior and complex wellbore geometry.

A sensitivity study of tool and reservoir parameters is presented. The results indicate that unlike the slug test, tool geometry greatly influences the dimensionless-pressure response of the closed-chamber test. Tool design guidelines are presented for extending the period during which the closed-chamber test behaves as a slug test and is suitable for analysis by type-curve matching with published slug-test results. The superposition results also indicate that assuming ideal chamber gas behavior does not significantly alter the bottoihhole-pressure (BHP) response.
A Comparison of Shaly-Sand Interpretation Techniques in the Mesaverde Group of the Uinta Basin, Utah
Authors: Chisholm J. L. , Schenewerk P. A. , Donaldson E. C.
Published: December 2007

The methods available for the interpretation of well logs in shaly sandstones are numerous. Deciding which methods to apply in a given area or formation is often difficult. A cation-exchange-capacity (CEC) correlation is presented for the Mesaverde group of the Uinta basin, Utah. Three porosity estimators are compared with core porosities. Nine water-saturation estimators are compared with Waxman-Smits water saturations.
Surfactant Flooding With Hard Water: A Case Study Solved by HLB Gradient
Authors: Minssieux Louis
Published: December 2007

Surfactant formulations were designed for field application of micellar processes in a salty environment on the basis of a mixture of one synthetic sulfonate with two types of nonionic agents. This formulation led to the required Winsor-III-type phase diagram in the presence of reservoir fluids at reservoir temperature. The main difficulty in this study was the high level of surfactant retention in the reservoir rock. The sacrificial agents tested did not reduce these surfactant losses significantly. The solution found to be efficient consisted of creating a hydrophile-lipophile balance (HLB) gradient of the additives used in situ by injecting a desorbing agent with high HLB behind the micellar slug containing the nonionic cosurfactants with lower HLB. The interpretation proposed for such a procedure shows that the mechanisms involved produce the same beneficial effects as the salinity gradient technique. The good results obtained indicate the potential importance of the HLB gradient when the salinity gradient cannot be used in the micellar processes under consideration.
Practical Considerations When Reservoir Boundaries Are Encountered During Well Testing
Authors: Moser H.
Published: December 2007

Semilog type-curve matching applied to drawdown, desuperposed drawdown, Miller-Dyes-Hutchinson (MDH), and Matthews-Brons-Hazebroek (MBH) plots can determine drainage shape and the outer boundary conditions of a well. Because only a single set of type curves for a particular drainage-shape/outer-boundary condition is necessary, the selection of a proper well-test model is straightforward.

Additionally, the porosity/compressibility/area product and the skin effect can be estimated with a semilog type-curve match. Furthermore, a generalized form of desuperposition has been applied when the duration of the buildup is a multiple of the drawdown period. This method eliminates the use of all drawdown pressures except at the moment of shut-in. Therefore, variable skin effect during drawdown (e.g., cleanup) can be analyzed.
Correlation of Oil Formation Volume Factor and Solution Gas-Oil Ratio
Authors: Knopp C.R. , Ramsey L.A.
Published: December 2007

Thermally-reduced oil formation volume factor is correlated with solution gas-oil ratio from 0 to 3,500 cu ft/bbl. This correlation was made from the differential liberation curves of 159 analyses of saturated Eastern Venezuelan crudes. Average error, determined by comparing correlation and calculated with the laboratory-determined oil formation volume factor, was found to be 2.00 per cent. Average error of 104 separator flash tests was 1.97 per cent.

Introduction

Based on the original method of Katz, a correlation of thermally-reduced oil formation volume factor and solution gas-oil ratio has been made from saturated Eastern Venezuelan crudes. The accuracy of this correlation, which requires a minimum amount of data and is easy to use, is sufficient for most reserves estimates. The average correlation error of 2.00 per cent for reservoir differential data compares closely with the 1.97 per cent error for separator flash data.

While the accuracy of this correlation for other oil-producing areas is not known, there is close agreement with the general correlation of Katz. Also, there is a wide crude-oil gravity range represented, 15 degrees to 47.5 degrees API, with reservoir temperatures that range from 142 degrees to 307 degrees F. It is thought, therefore, that this correlation can be universally applied with reasonable accuracy. Wherever sufficient data exist, a cross plot can quite easily be made so that an area-oriented correlation is obtained.

Construction and Error

Fig. 1 is a correlation obtained from 159 differential liberation curves of saturated Eastern Venezuelan crudes. This correlation closely parallels the Katz general correlation previously made to a maximum solution ratio of 1,300 cu ft/bbl. Data obtained from volatile Venezuelan crudes shows that this correlation can be extended to 3,500 cu ft/bbl with good data conformance. The extension of the correlation is almost linear. Data used in Fig. 1 represent crude oils which range from 15 degrees to 47.5 degrees API. Reservoir temperatures of these crudes range from 142 degrees to 307 degrees F.
Natural Convection in Porous Media and Its Effect On Segregated Forward Combustion
Authors: Dirksen C.
Published: December 2007

This study investigates whether oxygen consumption during segregated forward combustion may be affected by natural convection. Linear theory indicates that thermal instability occurs in a horizontal porous medium when the modified Rayleigh number N'Ra exceeds a critical value of about 40. Most experimental results, including those described here. indicate this value to be about an order of magnitude smaller. N'Ra is derived from "differential similarity" and the proper time scale factor is also obtained.

The critical value of N'Ra for a horizontal, water-saturated porous medium at atmospheric pressure subjected to a vertical temperature gradient was found to be about 3.0. The ambiguity in the value of N'Ra arising when fluid properties cannot be assumed constant is indicated. Natural convection was observed for oblique systems below N'Ra while simultaneous horizontal flow did not affect N'Racrit.

The expected range of values for the various parameters pertaining to segregated forward combustion is indicated and the corresponding values of N'Ra calculated. Only under very favorable conditions, such as high permeability, high pressure and low top temperature, can the critical value of N'Ra be exceeded. Thickness of the convection layer should not become too large. since the time required to obtain significant mixing is proportional to the square of the thickness. For an oblique combustion front the conditions for significant mixing may be less strenuous.

INTRODUCTION

Laboratory1,2 and field3,4 experiments have shown that a markedly upgraded oil can be produced by in situ forward combustion. Under certain conditions injected air may move through a high permeability, gas-saturated channel over the oil-saturated layer, while combustion takes place, exclusively, at the horizontal interface (Fig. 1). Such a channel may be a natural gas cap, or, it may result from a forward combustion process in which injected air and combustion gases fingered through the top of the formation, causing a premature breakthrough at the production well.

In this particular case of segregated forward combustion, the air stream moves parallel to the combustion front. Molecular diffusion and transverse mechanical dispersion will be insufficient to cause all the oxygen in the air stream to reach the combustion front. When the oxygen in the air stream is not completely consumed in the combustion process, it will reach the production well and create a serious fire hazard. In addition, the reduced efficiency may make the process economically unprofitable while also serious corrosion problems may be experienced in the production well.3 This undesirable situation should, therefore, be prevented.
Drilling the Cold Lake Horizontal Well Pilot No. 2
Authors: MacDonald Ron R.
Published: December 2007

Esso Resources Canada Ltd. drilled its second horizontal well at Cold Lake, this time achieving a 1016-m [3,333-ft] horizontal interval. Two key limitations—hole drag and wellbore position accuracy—required special attention. The well design and the methods planned to accommodate these limitations are compared with the actual well data.
Multiple-Contact Phase Behavior Measurement and Application With Mixtures of CO2 and Highly Asphaltic Crude
Authors: Bryant D. W. , Monger T. G.
Published: December 2007

This paper is an experimental study of the phase behavior relevant to CO2 flooding for multiple-contact miscible, immiscible, or huff 'n' puff applications. Unique features of this investigation are that the live reservoir oil was highly asphaltic and was modified to resemble the composition likely contacted by injected CO2. Single-contact and two types of multiple-contact PVT data are presented, and the usefulness of such data in predicting CO2 flood performance is discussed.

The results show no liquid/liquid/vapor (L/L/V) three-phase region at higher temperatures and no liquid/liquid (L/L) critical point. Large CO2 concentrations were required before substantial hydrocarbon extraction occurred. A ternary diagram representation of forward multiple-contact compositional results indicates that CO2 generated miscibility with the oil by the vaporization mechanism. Precipitation of a tar-like, highly aromatic solid was associated with the development of miscibility. This solid phase represented approximately 20 wt% of the stock-tank-oil hydrocarbon. The swept-zone multiple-contact results show a cumulative liquid volume production of about 35% of the original oil in place (OOIP) after the second CO2 contact, with further contacts recovering essentially no additional oil. The residual oil was composed of heavy, aromatic hydrocarbon.
Flow-Testing Coalbed Methane Production Wells in the Presence of Water and Gas
Authors: McKee C. R. , Bumb A. C.
Published: December 2007

When water pressure is lowered to allow coalbed methane to desorb and flow to the well, three distinct flow regimes can be identified: (1) saturated water flow with no gas phase; (2) unsaturated water flow with an immobile gas phase; and (3) two-phase flow of gas and water. This paper derives a solution that includes the first two regimes in a single formula. The concept of parameter measurement windows is introduced and applied to analyze data from Glover Well 1 Drawdown Test 2 to obtain additional information on relative permeability and saturation curves. An increase in slope, which was initially attributed to other causes, is explained as a relative permeability effect.
A New Digital Multiscale Pulsed Neutron Logging System
Authors: Randall R. R. , Gray T. P. , Craik G. C. , Hopkinson E. C.
Published: December 2007

A new multiscale pulsed neutron capture logging system (PDKSM-100) is discussed. The instrument is a 11116-in. [1.7-cm] -diameter, microprocessor-controlled logging sonde that processes raw data occurring in the short-and long-spaced detectors. The timing spectrum (10 μsec per channel and 100 channels for the decay component) of the detector events is accumulated downhole and transmitted to the surface computer logging system upon command by a pulse code modulation data transmission system. This configuration makes use of significantly increased count rates to improve log repeatability greatly. Unique data reduction techniques are also possible with the high-resolution data.

The gamma rays during the burst of 14-MeV neutrons are also processed. This unique feature allows derivation of the ratio of inelastic to capture count rates, which is a function of porosity.

All conventional pulsed neutron capture (PNC) responses can be observed with the new pulsed neutron logging (PNL) system. However, many additional aspects of formation evaluation are possible as well. Several of the more unique features of the system are demonstrated in specific log examples.
A Key to the Future - A Review of the Economics of the U.S. Oil Producing Industry
Authors: Priestman G. Dawson
Published: December 2007

Introduction

Most oil men are keenly concerned with the outlook for the domestic producer. Will production increase? Will profits improve? How long will spare capacity be a problem?

In seeking answers to these and similar related questions, the oil-producing industry needs a much clearer picture of long-term trends. Unfortunately, such a picture has not been readily available due largely to a lack of reliable industry data. But some things are obvious-over the last 10 years, expenditures have increased considerably and over-all profits on new investments have declined. This trend has raised many questions regarding the economics of the industry, and in recent years a new profession has appeared-exploration and producing economics. Basically, the function of the producing economist is to analyze the trends of the past to find "a key to the future".

This paper offers an analytical approach to the economics of the United States oil-producing industry over the past 20 years. While the methods used may not be fool-proof, they are believed to give a reasonable appraisal of the situation as it has existed.

Two basic factors, "income" and "expenditures", must be understood when analyzing an industry or a company. The relationship between income and expenditures gives "profit", the motivating force behind the free-enterprise system. These factors, although they sound simple, are often difficult to interrelate, especially in the petroleum industry. It is important that they be known and recognized, not only for individual or company use, but also in efforts to explain their significance to the public and to Congress.
Microcomputer Applications in the Drilling Industry
Authors: Berkson Brad , Shoham Ovadia
Published: December 2007

The popularity and usefulness of the microcomputers are rapidly increasing. This tool has many applications which are pertinent to the drilling industry. Software and hardware for drilling uses are finding their way into the field. Lotus 1-2-3 is one of the many microcomputer software packages that has uses in the drilling business. Two programs using Lotus 1-2-3 were developed in this study for application in drilling. The first is a drill bit hydraulics optimization spreadsheet, and the second is a graphics macro for generating curves of well depth vs. number of drilling days. Both programs demonstrate the distinct advantages of applying microcomputers in the oil industry.

Introduction

The recent boom in microcomputers has opened the avenue to many uses of microcomputers in the oil industry. Their applications in the drilling industry in particular are just now being realized. Micros can be used in all facets of the drilling business to do anything from economic planning and analysis to bit efficiency and Measurement While Drilling (MWD) monitoring. These computers can manipulate technical and economic data so quickly and cheaply that they are fast becoming invaluable in today's highly competitive economy.

Some of the advances applicable in the drilling field include: 1. Economic and Financial Applications. These applications are key to the main purpose of drilling-profitability. Current spreadsheet software can enable a drilling contractor to speed cash flow analysis, inventory control, and track revenue and expenses. Also, accurate records of equipment can be kept for both depreciation and maintenance purposes.
Operation of a Dry-Desiccant Type Hydrocarbon Recovery Unit
Authors: Drake Q.S. , Dawson E.R.
Published: December 2007

Introduction

The dry-desiccant type of hydrocarbon recovery and dehydration unit has been on the market in the oil and gas industry for several years, but not until the last few years have developments on the unit been such as to justify more than a passing glance. Prior to this, the operator's main concern was to dehydrate gas to meet the pipeline specification for water-vapor content; any distillate recovered was considered a bonus. That is not the case today.

Companies have come to expect this unit to "pay its way" and to show a profit beyond the initial cost of the unit, as well as to dehydrate the gas. There now is no reason for allowing heavy hydrocarbons to be delivered to a natural gas pipeline for a price which is about 1/20th of its value if recovered as a stock-tank product.

Structural Characteristics of the Unit

Though the main concern here is with the operational characteristics, it will be helpful to give a brief description of the unit. The unit is fully automatic, skid-mounted and (with the exception of the regeneration gas heater) is self-contained. (See Fig. 1.) In this operation, the gas flows from the wellheads to conventional high-pressure separators and into the unit. Here the gas alternately passes through two vertical adsorption towers, which are packed with silica gel, and goes from there to the gas sales line. While one tower is adsorbing the distillate and water, the other is being regenerated in preparation for adsorption. In the regenerating tower, the liquids are being removed from the desiccant by circulating heated regeneration gas. This heated regeneration gas causes the adsorbed liquids to vaporize and be carried out with the regeneration gas. These vapors are cooled through heat exchangers to a liquid state and separated in the regeneration gas scrubber. The separated liquids are then staged to a stabilizer tower (or to a low-pressure separator) and then on to the stock tank. The gas from the regeneration gas scrubber returns to the gas pump suction. Thus, this unit is operating by what is termed a closed regeneration system; i.e., the regeneration gas is in a separate closed system from the main gas stream and is used over and over for regeneration.
Liquid Propellant Stimulation: Case Studies in Shallow Appalachian Basin Wells
Authors: Watson S. C. , Benson G. R. , Fillo G. J.
Published: December 2007

Stimulation trials have been conducted on more than 87 oil and/or gas wells in the Appalachian basin with a new liquid propellant. The liquid propellant differs from high explosives in that it is not cap-sensitive and it exhibits a detonation velocity and shock-wave energy like a solid propellant. However, it differs from solid propellants in that it does not require center priming or water-tight containers and generates a high gaseous expansion energy per unit volume like an explosive.
Deep Hydraulic Pumping-Reno Field
Authors: Hollis R.G.
Published: December 2007

Hydraulic pumps set deeper than all other pumps in the world are producing at rates up to 3,400 BOPD in the Reno field, Wyo. The magnitude of producing rates, operating pressures and well depths provides interesting production engineering problems. This report is concerned with equipment design and layout for surface and bottom-hole pumping systems, and includes recommendations for optimum surface pumping equipment for future batteries. Operating problems associated with high-volume pumping from 15,000 ft are discussed, and plans are outlined for increasing production rates to more than 4,300 BOPD/well.

Introduction

Wells in the Reno field, located near Buffalo, Wyo., are particularly suited for casing-free hydraulic pumping because of their depth, high productivity and low GOR. Production problems have generally been handled by increasing the capacity of the production equipment and decreasing pressure drops in the system. The cost of hydraulic pumping equipment has been on the order of $100,000/ well for tae four completed wells. A study made in an attempt to reduce the cost of production equipment for future wells revealed the capital cost could not be significantly reduced for these 1,200+ B/D wells, but fewer, larger power oil pumps and. engines were recommended for future batteries to reduce operating costs, especially where fuel must be purchased. Since safety of the surface high-pressure oil-pumping system is important, the layout and design of the power oil system were carefully planned.

Initial Development

Recovery of 5,750 ft of oil during drill-stem test No.1 from Government Well 41X-24 in Jan" 1965, signaled the discovery of the Reno field. In Feb., 1966, the four completed wells in the Reno field produced an average of 8,465 BOPD from 15,000 ft. Casing-free hydraulic pumps are used for artificial lift. Development of the field is progressing with six rigs drilling in the area.

Fig. 1 is a schematic drawing of a typical well completed in the Minnelusa (Tensleep) formation. Two of the zones are very fine to fine grain sandstone with dolomitic cement, and the third zone is micro-crystalline dolomite with porosity due to vugs. Table 1 shows reservoir and PVT data of interest. The reservoir originally had a static BHP of 6,600 psi and a low 450 psi bubble point. The crude bad a 34.9° API gravity and a GOR of less than 100 at a 30 psig separation pressure.

The discovery well, perforated in only the two sandstone zones, bad an initial flowing rate of 800 BOPD, but then declined to a rate of approximately 530 BOPD (no water) with a 30 psig tubing pressure. Based on gradient curves, the flowing BHP was estimated to be 5,000 psi, indicating a PI of 0.3. Due to the low GOR, the well could not flow at rates much above 500 BOPD; therefore, artificial lift was installed to maximize production and aggressively determine the well's inflow performance relationships.
Micro-PVT Apparatus Without Mercury
Authors: Laugier Serge , Richon Dominique
Published: December 2007

A new type of PVT apparatus is presented that avoids use of mercury and works with small sample quantities up to 10,500 psia [72 000 kPa] and 392°F [200°C]. The equipment is fully automated and the PVT cell is light enough to be weighed with an analytical balance within 10−5 lbm [0.5 × 10−5 kg]. Efficient stirring inside the PVT cell is achieved by use of a magnet rotating in a magnetic field. Internal capacity of the PVT cell is varied by movement of a piston, the displacement of which is measured within 1 μm to perform very accurate volume determinations.
A New Organic Fluid-Loss-Control Additive for Oilwell Cements
Authors: Stout C.M. , Wahl W.W.
Published: December 2007

A new organic fluid-loss additive for neat and gel cement slurries has been developed for use in squeeze operations to provide controlled dehydration of the slurry and, thus, fewer job failures. In addition, this additive provides greater fill-up behind pipe, even in highly porous formations. This material is compatible with bentonite materials and all portland cements, and it does not retard cement setting times of Class A cements or adversely affect the physical characteristics of the set cement. It acts as a thinner for high-gel cements, facilitating their application. It is effective over a wide range of well conditions and should provide improved control of cementing treatments. It is believed that this additive may permit the adaptation of neat portland slurries and permanent completion techniques to conventional squeeze-cementing operations.

Introduction

During the past 15 years, many advances have been made in oilwell cement formulations and application techniques. Recent cement technology has been directed toward "tailor-made" cement systems that achieve low slurry weight, minimize mud contamination, improve pumpability and provide other properties which help overcome the multitude of problems involved in current cementing operations.

One property of conventional neat portland or retarded cement slurries which has merited considerable study has been filtration control. Particular emphasis has been placed on developing adequate testing equipment and procedures which will simulate temperature and pressure conditions encountered during a well cementing operation. Various additives or admixes, developed to impart low filtration characteristics to cement slurries, have lost favor since development of more rigorous but realistic testing procedures. Good agreement now exists between the many different research organizations, so that the current tests developed by API Committee constitute a realistic yardstick by which newly developed additives can be evaluated properly. Also, cement systems employing these additives can be used in actual field operations with a greater certainty of success than ever before.
Analysis of the Flow of Gas Through Low-Permeability Porous Media
Authors: Newberg Mary Aylward , Arastoopour Hamid
Published: December 2007

A computer program based on the continuity and momentum equations for prediction of the flow of gas through low-permeability porous media was developed. This program uses the FORSIM code, which is based on the method of lines and several integration algorithms. Transient gas flow rates predicted with the computer program were compared with Inst. of Gas Technology's (IGT's) data for both partially water-saturated and dry tight-sand core samples.
Calculation of Vertical Fracture Containment in Layered Formations
Authors: Fung R. L. , Vijayakumar S. , Cormack Donald E.
Published: December 2007

An analytic procedure for calculating vertical fracture extent in symmetrical trilayered formations was extended to multilayered, asymmetrical formations using a semianalytic technique. The fracture extents computed by this method were compared with those calculated with the finite-element method. It was found that even for modulus variations between layers as large as a factor of 5, the semianalytic procedure gave exactly the same results as the finite-element solution in a fraction of the computation time and with significantly less manual data manipulation. It is recommended that the analytic and numerical procedures be used in a complementary manner to calculate fracture-width profiles in layered formations.
DeMoss Flood Handles Early Water-Breakthrough Problem
Authors: Riley E.A. , Williams B.G.
Published: December 2007

Introduction

The DeMoss field located in Archer County, Tex., 7 miles southeast of Archer City, is being water flooded under a unitized program (Fig. 1). The correct name for the unit is "Strawn (Basal) Sand Reservoir Unit"; however, for brevity and convenience it will be called the DeMoss flood in this paper. The purpose of this report is twofoldit is a case history of waterflood operation, andit shows how the profit and ultimate oil recovery were increased by the use of equipment designed to handle large volumes of fluid.

Two features,very high vertical permeability andhigh horizontal-permeability variation in portions of the pay zone, are believed largely responsible for early and excessive water breakthrough during waterflood operations.

The possibility that this solution to the problem of excessive water production in water floods could be instrumental in the development and production of waterflood reserves, which otherwise may be uneconomical, has been an added stimulus in the preparation of the paper.

Primary Development and Production History

The discovery well, A.J. DeMoss No. 1 (Unit Well No. 3–1) was completed in Nov., 1949, in open hole from 3,598 to 3,608 ft, flowing 302 BOPD and no water. Rapid development on 10-acre spacing followed, resulting in 27 producers by June, 1950 (Fig 2). General completion practice was to drill a few feet into the pay section with rotary tools, run electric logs, set and cement either 5 - or 7 in. production casing in a lime cap over-laying the pay zone. The wells were then swabbed-in on a flowing status. Very few of the wells had the entire pay zone penetrated by the wellbore. Production by solution-gas drive first began to decline in Nov., 1950; consequently, small hydraulic-fracture treatments were applied to a majority of the wells during Jan., 1951. Primary production peaked at 35,674 bbl of oil in April, 1951, as a result of the frac jobs; then, it declined to a low of 3,150 bbl of oil by Jan., 1957 (Fig. 3). Primary recovery to Jan. 1957, was 1,101,039 STB. An investigation of records revealed that the A.J. DeMoss No. 14 (Unit Well No. 3–14) probably produced 35 per cent of the accumulated, total primary recovery. This high one-well recovery figure is a result of a mildly active water-intrusion in this area acting on this well only. During the primary life of the field, the water encroached updip toward this well, thus sweeping a reservoir area greater than the normal well location. This will logically explain the very high recovery figure for the well.
Gas Invasion and Migration in Cemented Annuli: Causes and Cures
Authors: Stewart R. B. , Schouten F. C.
Published: December 2007

A laboratory study has been conducted to identify the various mechanisms involved in the invasion and migration of formation gas in cemented annuli and to develop procedures to stop this process. Mechanisms operate differently in different circumstances, and it is important for the zonal-isolation characteristics of the cement that the preventive procedures used are the appropriate ones.
Dynamic Pore Pressure Ahead of the Bit
Authors: Peltier Bertrand , Atkinson Colin
Published: December 2007

An analytic approach is presented in an attempt to improve the understanding of the mechanism of pore-pressure invasion ahead of the bit during drilling. An axisymmetric model accounts for a zone of damaged permeability (skin) on the work front. The effect of rate of penetration (ROP) and rotation speed on the pore pressure at the depth of cut is significant in the lower range of permeabilities, while for the high permeabilities, the skin has an overwhelming control on the pressure invasion.
Simultaneous Underground Gas Storage and Secondary Oil Recovery
Authors: Burke William F.
Published: December 2007

The Ambassador and New York City fields in Clay County, Tex., both of which produced from the Mississippian lime, are two depleted oil fields now being used for the underground storage of natural gas. Both of these fields are recovering substantial quantities of crude oil as a result of the high-pressure gas injection under the gas storage operation. The histories of these fields prior to the storage operations, the reasons for their selection as underground storage reservoirs and their performance both as storage fields and secondary recovery projects are reviewed.

Introduction

The basic function of a gas transmission company is to provide adequate service to its customers under any given load condition. This requires that the gas company contract for sufficient supplies of gas to meet its maximum demand under peal load conditions and provide adequate facilities to move such gas to its markets in the required quantities. Sufficient underground storage will allow the purchase and storage of gas in low-demand periods and the delivery of such gas to markets in the required volumes in periods of high demand. The high-pressure gas transmission lines of today are expensive, and it is extremely important that underground storage fields be geographically situated so that gas can be moved closer to markets in these low-demand periods through existing pipeline facilities. If underground storage can be combined with secondary oil and/or condensate recovery, liquid hydrocarbon recoveries can greatly reduce the over-all cost of underground storage.

Considering the fact that, in the period from 1942 through 1950, our annual system gas purchases had grown from 67,415 MMcf to 150,821 MMcf and anticipating continued rapid growth of the system (particularly the principal market, the Dallas-Fort Worth area); it became apparent that costly additional pipeline facilities to adequately service such growth would soon be necessary.
Rheological Properties of Daqing Crude Oil and Their Application in Pipeline Transportation
Authors: Yan Dafan , Luo Zheming
Published: December 2007

The variation of the rheological properties of Daqing waxy crudes with their thermal history and their time effect are discussed. Rheological properties of Daqing crude were determined in the laboratory with rotational viscometers and U-tube devices. The feasibility of using the proper heat treatment to improve the low-temperature flow property of Daqing crude was studied. Field tests on three long-distance heated-crude pipelines showed good agreement with laboratory measurement. A mathematical model for determination of the optimum operation parameters of pipeline transportation is also given.
Interpreting an RFT-Measured Pulse Test with a Three-Dimensional Simulator
Authors: Lasseter T. , Karakas M. , Schweltzer J.
Published: December 2007

An interpretation procedure has been developed to analyze repeat formation tester (RFT™) pressure surveys quantitatively during well-to-well interference tests with a three-dimensional (3D) simulator in which only the pressure equation is solved, while retaining saturation effects on fluid viscosity and relative permeability. This approach accurately and efficiently determines location and transmissibility of faults, horizontal permeability of production zones, and vertical permeability of barriers over length scales comparable to reservoir dimensions.
Physics of Blob Displacement in a Two-Dimensional Porous Medium
Authors: Lenormand Roland , Zacone Cesar
Published: December 2007

The evolution of the geometry of blobs is observed during displacements in a two-dimensional (2D) transparent micromodel, and such macroscopic parameters as pressure drop and recovery are monitored simultaneously. The results are in good agreement with experiments performed in real media and with theoretical calculations of the conditions required for blob mobilization when the presence of loops in the structure is taken into account.
Detecting Fluid Movement and Isolation in Reservoir Core With Medical NMR Imaging Techniques
Authors: Baldwin B. A. , Yamanashi W. S.
Published: December 2007

A medical nuclear magnetic resonance (NMR) imaging instrument has been modified to image water and oil in reservoir rocks by the construction of a new receiving coil. Both oil and water inside the core produced readily detectable hydrogen proton NMR signals, while the rock matrix produced no signal. Because of similar NMR half-lives, the water was doped with a paramagnetic ion, Mn+2, to reduce its relaxation time. This procedure enhanced the separation between the oil and water phases in the resulting images. Sequential measurements, as water imbibed into one end and oil was expelled from the other end of a core plug, produced a series of images that showed the location of the fluids as a function of flow time. For water-wet Berea sandstone, a flood front was readily observed, but some of the oil apparently was left behind in small, isolated pockets that were larger than individual pores. After several additional PV's of water flowed through the plug, the NMR image indicated a homogeneous distribution of oil. The amount of residual oil determined from the ratio of NMR intensities closely approximated the residual oil saturation of fully flooded Berea samples measured by the Dean-Stark method. A Berea sandstone core treated to make it partially oil-wet did not show a definitive flood front but appeared to channel the water around the perimeter of the core plug. The relative ease with which these images were made indicates that NMR imaging can be a useful technique to follow the flow of oil and water through a core plug for a variety of production processes.
Evaluation and Comparison of Residual Oil Saturation Determination Techniques
Authors: Chang M. M. , Maerefat N. L. , Tomutsa L. , Honarpour M. M.
Published: December 2007

The amount and distribution of residual oil saturation (ROS) are critical parameters for determining whether to apply an EOR process to a reservoir. A brief review of available ROS techniques is presented, indicating advantages, limitations, problems, and possible improvements of each technique. Advantages and disadvantages of each ROS-determination technique are summarized. Screening criteria for determining the best ROS technique under certain wellbore or reservoir conditions are presented.

This paper also presents results from comparisons of ROS measurements obtained from the literature as calculated from resistivity logs, pulsed neutron capture (PNC) logs, pressure coring, single-well tracer tests, nuclear magnetism logs (NML), carbon/oxygen (C/O) logs, and electromagnetic propagation tool (EPT) measurements. In this study, the ROS measured by each method is compared with that determined by other methods conducted in the same well. The comparison shows that average values of ROS determined by C/O log, PNC-LIL (log-inject-log), and single-well tracer test do not differ statistically when compared with other methods. The resistivity log tends to give higher than average [2 saturation units (s.u.)] ROS measurements, while pressure coring tends to give lower than average (4 s.u.) ROS values. EPT and NML show deviations of about 8 s.u. of ROS values from other methods, which indicates a statistically significant difference.

ROS vertical profiles obtained by two different methods from the same well were compared to eliminate the ROS variation resulting from formation depth. The vertical profiles based on ROS zoning and foot-by-foot measurements were studied to provide more "resolution" for comparisons. The results show that discrepancies in measurement methods are more pronounced when vertical profiles are divided into different zones. This could mean that the discrepancies are much greater for some zones than for others. This approach offers the possibility of studying ROS-method discrepancies as a function of different ROS values.
Effectiveness of Screening Tests as Predictive Models for Steamflood Additives
Authors: Strycker Arden R. , Madden Michael P. , Sarathi Partha
Published: December 2007

The control of fluid mobility has become increasingly important to steamflood applications for oil recovery. Most of the EOR projects in the U.S. use steamflooding techniques. The efficiency of these projects is often reduced because such effects as gravity override result in poor volumetric sweep through the reservoir. Additives can improve the efficiency of steamflooding, but screening tests must be performed for selection of the most effective additive for individual applications. As potential additives, nine commercially available sulfonate surfactants were tested with the high-temperature/high-pressure foamability (HTHPF) test procedure, and eight of these were tested with the mobility control (MC) procedure. These surfactants were evaluated at 250 and 425°F [121 and 218°C] in deionized water and in 1% added NaCl. A correlation trend was also found between foam stability measured by the HTHPF test and mobility reduction measured by the MC test. This trend was evident for more than one type of sulfonate at both temperatures; an increase in temperature corresponded to a decrease in foam stability and mobility reduction. The dependence of foam stability on the presence of added NaCl varied from surfactant to surfactant.
Phase-Behavior Correlation for High-Salinity Surfactant Formulations
Authors: Chou S. I. , Bae J. H.
Published: December 2007

Many reservoirs targeted for surfactant flooding contain high-salinity brine. When preflushing such reservoirs proves unsatisfactory or uneconomical, it is essential to have surfactant formulations optimized for the reservoir brine. To minimize experimental effort in formulation design, we developed a theoretical model that can quantitatively predict the phase behavior of surfactant formulations mixed with oil. The model considers the effect of salinity, surfactant, alcohol, and oil on the geometry of the interfacial surfactant layer in microemulsions. The phase behaviors of five salt-tolerant surfactants — ethoxylated sulfate, two ethoxylated sulfonates, ethoxylated carboxymethylate, and alpha-olefin sulfonate — with a series of n-alkane oils (C6 through C16) and short-chain alcohols (C4 through C6), were studied and used to evaluate the theory. The optimal salinities of the systems studied ranged from 1 to 22% NaCl.

Model calculations of optimal salinity and solubilization capacity at optimal salinity show excellent agreement with experimental data. The well-known curves of solubilization vs. salinity, which cross over at the optimal salinity, are quantitatively produced for the systems investigated. In addition, the model correctly predicts the transition from lower- to middle- to upper-phase microemulsions as salinity is increased. Hence, it can be used as the basis of a compositional model in surfactant flooding.
Xanthan Stability at Elevated Temperatures
Authors: Seright R. S. , Henrlcl B. J.
Published: December 2007

Xanthan stability is examined to define more clearly the polymer's temperature limitations as a mobility-control agent. Experiments were performed to probe the relative importance of hydrolysis, oxidation, and helix-coil transitions in xanthan degradation. In the absence of oxidizing agents (i.e., dissolved oxygen), results indicate that free-radical, oxidation/reduction reactions are not the dominant mechanism for xanthan degradation. Depending on the pH, acid-catalyzed hydrolysis and base-catalyzed fragmentation reactions may play important roles. With Arrhenius calculations, it was estimated that under ideal conditions (no dissolved oxygen, pH 7 to 8, and moderate to high salinities), a xanthan solution could maintain at least half of its original viscosity for a period of 5 years if the temperature does not exceed 75 to 80°C [167 to 176°F], New polymers will be needed for chemical floods where xanthan does not have sufficient stability.
Effect of Wettability Alteration on Water/Oil Relative Permeability, Dispersion, and Flowable Saturation in Porous Media
Authors: Wang F. H. L.
Published: December 2007

Wettability alteration was shown to affect strongly water/oil two-phase flow behavior in Berea and Loudon reservoir cores. Two examples of wettability alteration were realized by core aging and core extraction. With a steady-state method coupled with tracer analyses, these changes in wettability were shown to affect relative permeabilities, dispersivities, and flowable saturations in the cores. The changes in wettability were also confirmed by waterfloods and spontaneous-imbibition tests.

Dispersion in steady-state two-phase flow was found to be a strong function of saturation and wettability. Dispersivity of each phase increases with decreasing phase saturation. Flow of the non wetting phase was dispersed much more than that of the wetting phase.

A large fraction of the nonwetting-phase saturation was found to be bypassed or nonflowable, while the wetting phase was completely flowable. The correlation between the flowable phase saturation and in-situ phase saturation was strongly affected by wettability alteration.
Tubingless Completions: A Review of Equipment, Economics and Techniques
Authors: Muse John F.
Published: December 2007

The economic advantages in completions utilizing 2%-in. tubing as casing are, generally speaking, quite obvious. In today's atmosphere of rising costs and increased competition, this completion method is being viewed with interest by practically every operating company. The number of completions actually made has increased greatly in the past year. It will increase even more when companies not now experienced with this type of completion are made aware of the methods successfully being utilized and the equipment being made available.

Companies interested in starting a program of tubingless completions are naturally concerned with the results which have been achieved in the past. They are also concerned with the difficulties that have been encountered. They want to know the savings that actually have been made in these completions and, also, what possible ultimate savings are now predicted. They want to know which methods and equipment have been tried and which have proved most successful. Also, they want to know what major problems still are unsolved and what limitations are becoming apparent.

In a rapidly developing technological change such as this, periodic reports are necessary to keep the industry advised of the progress made. This paper attempts to report the latest equipment, how it is being utilized, and what problem areas are evident.

Introduction

To date, most of the work done in the United States in tubingless completions has been performed in relatively shallow areas where production could adequately be handled by the 2%-in. casing. These areas are Southwest Texas, West Texas, the Texas Panhandle, Kansas and Oklahoma.

Many companies in these areas were contacted for information concerning the methods and equipment which were being utilized most successfully and, also, concerning the general economic results obtained. This permits the presentation of a wider scope of information than would a review of one company's results and methods in one area only; however, it presents somewhat of a reporting handicap because the information obtained must be discussed in general, rather than specific, terms.
Effects of Pumping Equipment on Sand-Laden Slurries
Authors: Roll D. L. , Himes R. , Ewert D. P. , Doerksen J.
Published: December 2007

Effects of pumping equipment, gravel-packing devices, and fracturing equipment on proppants and fluids were investigated. Generation of fines was not significant, but some crosslinked gels were severely damaged by shearing forces in the equipment.
Comparison of Steady- and Unsteady-State Flow of Gas and Foaming Solution in Porous Media
Authors: Huh D. G. , Handy L. L.
Published: December 2007

Relative permeabilities of foaming-agent solution/nitrogen gas were measured by steady- and unsteady-state methods in Berea sandstones. Results show a significant difference between steady- and unsteady-state flow. Unsteady-state experiments show a small change of relative permeability to gas over a wide range of saturations and exhibit no complete blocking effect. In steady state, however, the simultaneous flow of liquid and gas could be stabilized only above a minimum gas saturation of about 35 to 40%, probably because of the formation of a large number of foam lamellae by the continuous supply of foaming solution. The permeability reduction factor calculated from the ratio of the gas permeability in the presence of foaming agent to that in the absence of foaming agent is mainly a function of lamellae stability.

Pressures as a function of distance were measured at three pressure taps spaced at equal distances along the core. The pressure history shows abrupt jumps in pressure with advancement of the gas phase owing to capillary pressure. After gas breakthrough, the pressures at each tap were stabilized. The results during steady-state flow showed that the pressure gradient increases with increasing distance from the inlet end of the core sample, indicating that the higher gas fraction results in a greater blocking effect.

The surfactant effluent concentrations were measured by a UV spectrophotometer to calculate the adsorption isotherm of this foaming agent. The dynamic adsorption of Suntech IV™ showed a Langmuir-type isotherm. The adsorption was < 2 μmol/g sand for up to 1.0% concentration.