In the early stages of development of any process which fills a long felt need, there may be a number of improvements or refinements of a major nature if an aggressive research program is maintained. With usage and the adaptation to more applications, the actual magnitude of possible improvements in materials becomes less and less. Stated otherwise, when a process is deemed adequate, successive increments of improvement becomes less important. Such is the case with well stimulation. It should not be implied that further research or investigation is unjustified. On the contrary, much remains to be done. As long as there are areas that do not respond properly to existing materials and techniques, there is room for improvement. The possibility of a major improvement in present processes is limited. However, there are excellent possibilities for the development of an entirely different approach to the field of well stimulation.

Paraffin and/or asphaltenes are part of the oil that is produced from all the formations in West Texas. They are stable in the untouched reservoir. but once production begins, natural and maintenance caused deposition of these oil components can occur. The deposits can reduce permeability. plug pore throats or cause changes in wettability that can drastically reduce production. This paper will cover the chemistry of the deposits, causes of deposition and removal methods. Case histories of treatments of West Texas wells will be included.

The use of electric motors as prime movers for driving oil well pumping units is well established today. In fact, reliable estimates now indicate that a sizeable majority of new oil wells going on artificial lift are being powered by electric motors. With the tremendous increase in the use of electrified oil well pumping, many operators are examining their horsepower sizing and application formulae more closely than ever in using electric motors to drive beam pumping units. Field tests, for example, generally have shown that most electrified wells are over-motored and that economy of operation, as well as lower first cost, could be realized with a proper sizing of the motor to the load. Also, there is the question of which type of motor should be selected. There is general interest in the industry today in the evaluation and advantages in the performance of various design types of oil well pumping motors.

One of the questions often asked of the ESP manufactures is "What is the maximum GOR your pump can handle?" As stated this question is impossible to answer. One of the limitations of centrifugal pumps is their inability to handle significant quantities of gas. However because of the configuration of the pump and the nature of its application, the question of its limits is extremely complex. This paper examines how the presence of free gas affects the operation of the ESP's and looks at some of the techniques used in selection of pumps for gassy wells

This paper demonstrates the application and design of vapor recovery systems and the practical aspects and increased product value realized from the use of such systems.

In recent years programmable logic controllers (PLCs) have evolved to such a point that it is often technologically desirable and more economical to apply them preferentially over hard wired relays in the small control systems typically found in oil field production facilities. This paper will provide a short history of PLC development, describe the features and capabilities of PLC"s, examine possible applications for small PLC's in oil field production operations, and illustrate several applications.

For decades the oil industry has attempted automation projects with mixed success. The mechanical nature of most electrical components and the short shelf life of first generation electronic components brought many early automation attempts to partial or total frustration. And then came the integrated circuit (IC). This microminiaturization allowed us to travel to the moon and back, to replace slide rules with light powered business-card-size calculators, to enjoy coffee brewed for us in the moments just before we awake and so on. This same technology is now at work in our watches, cars, televisions, typewriters, radios, homes and offices...touching us through nearly every aspect of work and play with reliability second to nothing that precedes it. Seeing this technology as filling a much needed gap C-E Natco has selected from the highest end of the quality spectrum a programmable logic controller (microprocessor) and coupled it with the thousands of man years of design fabrication, operation and troubleshooting experience to create hardware/software packages capable of performing the demanding tasks of a demanding industry. These systems operated LACT units, vapor recovery systems, filter plants, burner firing and shutdown systems, steam generators and a host of others...with the emphasis on reliability.

This paper will present results of a field slippage test and compare these results with laboratory testing of pump slippage presented in the 1998 Southwestern Petroleum Short Course paper. This is progress report #2, with the ultimate goal being to present an empirical equation which will accurately represent the down-hole slippage. The current results should be useful to operators for selection of clearances between metal plungers and barrels.

This paper will present results of two field slippage tests and compare these results with laboratory testing of pump slippage presented in the 1998 Southwestern Petroleum Short Course paper and field application of larger clearance pumps. This is Progress Report #3, with the ultimate goal being to present an empirical equation which will estimate the down-hole fluid slippage over a wide range of pump clearances. Utilizing the field test data an empirical equation is presented. The current results should be useful to operators for selection of clearances between metal plungers and barrels.

This paper will present the results of the last down-hole-rod-drawn pump fluid slippage testing recently completed at the Texas Tech test well (Red Raider #1). This is # 4 in the series which began with laboratory testing presented in 1998. This paper will present an update to the empirical equation which will estimate down-hole fluid slippage over a range of pump sizes, clearances and strokes per minute (SPM).

Since patenting the idea of Progressing Cavity Pumps in the early 1930's by RenC Moineau, there have been few improvements to the original design of this pump to facilitate expansion of the range of application. There have been dramatic improvements in the elastomer industry and these new elastomers have been incorporated into the stators using the original design. Recently the Geremia brothers, of southern Brazil, perfected a radical new design in this relatively "simple" technology that will allow PCP's to enter into a whole new range of performance criteria. This new design is being termed the "Metallic Stator" due the fact that much of the elastomer has been replaced with steel alloy leaving only a thin, even layer of elastomer, which is supported evenly around the inside perimeter by the base metal in the tubing. This provides the industry with numerous advantages over the conventional PCP's including: Higher pressures, lower torque"s, shorter pumps, fewer sizes, harsher environments, lower power requirements, and higher flow rates. In addition to the conventional method of driving this pump from the surface with sucker rods, this metallic stator has now been incorporated into a sucker rod free hydraulic design that can be pumped into place downhole, operated, and returned to the surface with only the use of power fluid and the proper well head valving arrangement.

Results of a field test study proved that progressive Cavity (PC) pumping systems provide greater mechanical efficiency and less electrical usage than beam and electrical submersible pumping (esp) systems in mature waterflood producing wells. These systems were evaluated in Permian Basin wells ranging from 3800 feet to 5000 feet in depth and production rates ranging from 500 barrels per day to 1000 barrel per day. Operating facilities were used to monitor production, fluid shots were used to monitor fluid levels, and inline mechanical kw-hr meters were used to measure electrical usages before and after PC pump system installations. Mechanical efficiencies were calculated based upon this data. Production tests indicate that total well productivity was increased and an incremental oil increase was realized where PC pumping systems replaced beam lift systems previously thought to be optimum. Increased water production due to waterflooding has necessitated lift revisions and beam pump optimization. When a beam lift system has reached maximum potential, a larger lift system becomes necessary. Esp systems provide increased lift capability, but at a much lower efficiency. The criteria used for selecting the test wells was maximized beam lift and economically marginal esp producing systems. The purpose for the field test was to determine if PC pumping systems were an economic alternative to lift these high WOR wells when compared to beam and esp systems. A field test study was began in 1991 to evaluate mechanical and electrical efficiencies of PC pumping systems in the environment stated above. A comparative analysis to beam and esp lift systems was then performed. This paper presents the results of that analysis and confirms that PC pumping systems are the most cost effective artificial lift systems in mature Permian Basin waterlood producing wells.

Most exotic fluids introduced into a reservoir will cause reduction in permeability near the wellbore. Dispersed water base fluids and oil base fluids create their own unique problems, such as wettability changes, and emulsions. Prior knowledge of what drilling fluids can do to a formation will, upon completion, lead to a better diagnosis of well behavior and thus resulting in more effective clean-up and stimulation procedures. Hydrochloric acid (HCL) as a stimulation fluid has been and continues to be misused as a method to increase reservoir permeability. Incorrect application can either create a problem greater than the original and/or cause unnecessary expense to the operator. The cause of productivity impairment should first be determined before a stimulation procedure is selected. Scanning electron microscopy, X-ray diffraction, thin section petrography and core-flood analysis are effective techniques in determining the sensitivity of a reservoir to foreign fluids. Rock-to-fluid and fluid-to-fluid compatibility tests are extremely important to improve stimulation procedures and to ultimately improve production. As money for drilling and completing wells gets scarce, proper utilization of current technology can result in a higher return of investment.

Artificial Lift Systems are under constant attack from storms, load and utility grid switching and internally generated switching. The associated voltage phenomena are cumulative in nature and degrade the integrity of these electric/electrical powered systems. The cost associated with adding equipment which is designed to protect system from this type of damage is far less than the cost encountered when attempting to recover from the damaging effects.
When using Variable Frequency Drives (VFDs) in ESP and Rod Pump applications many benefits can be realized, however an increased level of awareness regarding a properly designed electrical system is needed. Input and output waveforms are distorted by the very nature of VFD technology (fixed speed AC input current / variable speed AC output current). The use of properly selected and coordinated protection, such a secondary surge suppression and chemical grounding, can effectively minimize the negative effects (increased system total cost of ownership, loss of production) of premature equipment failure due to voltage irregularities inherent to the system.

The importance of proper procedures, well data coordination, communications, subcontractors and employee training for submersible pump operations cannot be overstressed. This paper points out how some operating practices can result in unnecessary expense, and provides recommendations for helping to reduce these costly mistakes. It is felt that if these recommendations are followed, it will result in highly successful submersible operations for the user. It is recommended that the producing company evaluate the points of this paper and put into action the good working practices and training that will result in efficient operations with good economical results.

Attent ion to proven des ign parameters, such as are used to design plant process equipment, can improve the operation of petroleum production systems. A review of the development of primary extraction devices is given, along with formulae for efficiency and allowable velocities. Vane type, wire mesh and centrifugal are examined. Staggered baffles and zig-zag or wave plates are discussed. Design criteria for the application of these primary elements are compared, thus allowing the selection of the optimum type mist extractor for most desired services. The influence of liquid loading/entrainment on separator sizing is discussed. Vessel dimensions and liquid capacity are related for each type of primary element. It is shown how comparisons of advantages can help make an economic selection for any given problem.

Indiscriminate selection of production logging tools through haste or lack of knowledge has often resulted in inadequate or incomplete information on down-hole fluid movement. With the proper selection of tools through knowledge of both tools and well problems, more information can be obtained. A comparison of tools and methods is presented providing procedures which can be utilized for optimum analysis of down-hole fluid movement.

Proper cleanout of millscale and other iron oxides from new tubular goods prior to their use reduces production damage by deposition (in the producing formation) of iron solids and iron in solution. Iron removed from new tubulars by stimulation fluids has caused formation damage and reduced production for many decades. This iron is available for removal from the walls of the casing and tubing by the action of stimulation acids and erosive proppants being pumped to stimulate the well. The sources of this iron are listed below. 1. Millscale (magnetite) is a thin layer of iron oxide found on the surface of tubulars. Millscale is deposited as a result of cooling the tubular steel after heating and extruding processes are done. 2. Iron oxides have many forms, but are basically rust. Although numerous iron scales are encountered in oilfield operations, and many are contacted by stimulation fluids, they are by-products of oil and gas production. Millscale and rust arrive on location with tubing and casing, and there is little doubt that the problem exists on most locations. This paper presents a method to "pickle" tubulars to help eliminate the source of many iron deposition problems.

In the early stages of production of oil in the Pennsylvania and West Virginia fields, very little, if any, "bad oil" or emulsions were found. The small amount that was made created a very minor problem. The reason for this small amount of emulsion was due to the fact that oil produced in these fields was almost void of any foreign matter. Also, what water was produced was almost pure and very little gas was found. This kind of condition will not make an emulsion. This will be explained later.

A discussion of the properties and sensitivities of high strength tubular goods outlining selection and handling criteria which must be followed to assure satisfactory performance. High strength correspondingly reduces ductility of these steels causing them to be particularly susceptible to defects and corrosion.

During the past several years, production and service companies have been trying to solve an old problem that occurs after fracture of productive zones in the Permian Basin. Many solutions have been used with little or no success to prevent proppant flowback. The problem of proppant flowback occurs in both cased hole as well as open hole completions. New applications using old completion technology have been applied recently to improve control of proppant flowback. The technology used was developed from sand control methods dating back to the 1g70 t s. 1,2,3,4 These methods consist of slurrying the same mesh sand used during the fracturing process with a resin. This yields a complete sand resin and catalyst mixture to ensure proper setting of sand. The ability to alter the catalyst makes it an attractive alternative due to the wide range of pump times available. The original slurry was developed to place an artificial zone in a hard rock, open hole environment following a propped fracture treatment. The slurry is allowed to set up and then drilled to a size known to be smaller than the original open hole section. This will give a permeable ring of resin-set sand to prevent proppant from flowing back into the wellbore. The liquid resin squeeze technique, used in a cased hole application, was conceptually designed to utilize the in-place proppant material. This resin bonding of the proppant will create a permeable barrier preventing proppant flow into the wellbore. This paper will describe, in detail, a case study of a field in West Texas and how to prevent proppant flowback in both open and cased holes using slurried resin and sand. It will also evaluate the well's performance.

There are many types of proppants and mesh sizes to consider in the design of a fracture stimulation treatment. When considering proppants, sand (Ottawa, Texas Mining, Unisil), bauxite, intermediate strength proppants (ISP), resin-coated sand (RCS), precured resin-coated sand (PRCS) and Z-prop, the principal questions seem to be, "Which one do I select and how should I use it?" Maximizing adequate long-term productivity in low-permeability reservoirs is dependent on both fracture penetration and fracture, conductivity. How to obtain deeply penetrating fractures, contained and adjacent to the porous interval, is one of the problems that challenges the industry. The other is how to obtain sufficient fracture conductivity to effectively utilize the deep penetration. This paper discusses how to determine and obtain sufficient fracture conductivity. Fracture conductivity is a function of the proppant properties (i.e., strength, roundness, fines content, etc.), closure stress, drawdown rate, formation properties (i.e., proppant embedment conditions) and resultant propped fracture width. The engineering principles involved in the selection of the proper type and amount of proppant are supported with a case history. This is a "state-of-the-art" paper, attempting to bring the current technology on proppants together in one place.

For worthwhile oil or gas well stimulation the best proppant and fluids have to be combined with a good design plan and the right equipment. Proppant selection is one of the important areas which determines how worthwhile and how successful the stimulation treatment can be. To select the best proppant for each well a general understanding of available proppants is imperative. Also, the latest proppant properties for design are taken at downhole conditions with embedment, temperature, crushing and long term effects all being considered. After downhole permeability of a proppant is measured, it becomes a logical process to narrow the selection of the proppant to a particular class and sub-class. With information from the downhole formation or reservoir the proper mesh size can be selected to fix the specific proppant, and optimize the hydraulic or acid fracturing treatment on the well.

Proppant spillage from mobile proppant conveying units used on fracture sites has been an ongoing problem industry wide. With the spillage of the proppant comes the inability to control the flow, levels in blending equipment, and the creation of dust.
Currently mobile proppant conveying units are being operated by turning the conveyor belt to its maximum speed and the material discharge slide gates are opened at various intervals to control the amount of proppant to be placed on the conveyor to be discharged by the unit. The proppant material often overflows off the sides of the conveyor when discharged from the dispensing unit. The material overflow can freeze the conveyor belt from moving.
This paper introduces a solution that solves the problem of proppant spillage from a mobile proppant conveying unit, it also reduces dust from the conveying unit, and creates a better job operation environment for the equipment operator.

A method is presented for predicting the transport of proppant in a fracture during a hydraulic fracturing treatment. In addition, the settling of the proppant during closure of the fracture following the treatment is considered. From the final distribution of proppant, increases in well productivity (stimulation) are calculated. The examples given illustrate that proppant settling during fracture closure can determine the success or failure of a hydraulic fracturing treatment.