Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
Introduction It was concluded in a previous study that for an electric submersible pump to operate effectively and efficiently while pumping gaseous fluids, the amount of free gas ingested into a centrifugal pump must be maintained at low values. This can be accomplished either by increasing the submergence pressure on the pump intake or by mechanically separating the free gas from the fluid to be pumped. This study presents data for the performance of a reverse-flow and a centrifugal type gas separator attached to a centrifugal submersible pump. The results of two independent test programs are presented. One program used water and air as test fluids. and the other test results were obtained using diesel fuel and CO. Principles of Separator Operation Reverse-Flow Separator The reverse-flow separator depends on buoyancy and surface tension effects and a sharp flow reversal to accomplish its free gas separation. Cross sections of both a reverse-flow and a centrifugal separator are shown in Fig. 1. The reverse-flow type consists of housing intake ports located above the inner intake ports. This configuration causes the inlet flow to make a sharp 180 deg. bend, thus allowing some free gas separation at the housing inlet ports. The upturned impeller will produce some head and assist in allowing the pump to recharge itself with liquid if it becomes gas-locked. If the pump gas locks because of either an accumulation of free gas or a large gas slug, the fluid will fall back through the upturned impeller, thereby allowing this impeller to recharge the first regular pump stage. This reduces the number of electrical shutdowns of the unit by the underload protection device. Centrifugal Separator The centrifugal gas separator as shown in Fig. 1 consists of an inducer and a high-capacity, highly mixed-flow pump stage followed by a separator chamber. The inducer and pump stage are incorporated to provide sonic means to overcome the resistance of the internal flow and vent passages. Both inducer and pump stage underwent separate testing and showed the capability of generating a small amount of head without surging with fluids of high free-gas content. The separator chamber consists of a rotating unit with radial vanes and an integral outer shell, The rotating outer shell of the chamber is a significant feature of this separator. It provides a radially closed chamber where flow-shearing or turbulence are minimized because the fluid rotates with the chamber as a solid body. The cross-sectional area of the chamber is kept as large as possible to keep the axial flow velocity minimal, thereby allowing the maximum residence time in the chamber, where it is acted on by intense centrifugal acceleration forces. The heavier Hubs accumulate near the outer wall. and the free gas accumulates near the shaft because of these forces. These fluids then are separated physically in the top section of the separator chamber and are ducted to the first pump stage. The gases are vented to the casing annulus by use of a crossover diffuser. Test Facilities and Procedures for Diesel Fuel/CO Tests The performance tests for Centrilift-Hughes Inc. were conducted by the R.C. Ingersoll Research Center. A schematic of the test facility is shown in Fig. 2. A 20-ft section of 6-in. annulus casing was installed above the pump discharge. At the top of this casing a vent and gas metering section were added. The pump and separator were installed in the 8-in. housing as shown. The unit was tested on a mixture of diesel fuel and CO. The CO was injected into the inlet flow line to the test loop housing and was vented at the top of the annulus casing. JPT P. 1327^
- Research Report > New Finding (0.46)
- Research Report > Experimental Study (0.46)
- Reservoir Description and Dynamics (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring (1.00)
- Production and Well Operations > Artificial Lift Systems > Electric submersible pumps (1.00)
- Facilities Design, Construction and Operation > Processing Systems and Design > Separation and treating (1.00)
A Revolutionary Packer Type Gas Separator that Involves Gravity Force to Exceed Traditional Gas Separation Efficiency in Oil and Gas Wells
Gonzalez, Gustavo (Odessa Separator Inc) | Guanacas, Luis (Odessa Separator Inc) | Portilla, Carlos (Odessa Separator Inc) | Vazhappilly, Neil Johnson (Odessa Separator Inc)
Abstract A revolutionary packer-type gas separator was designed to improve downhole gas separation efficiency. A deep analysis of gas separation methods was done to understand the process's nature and design a tool that could generate enhanced conditions for the gas separation phenomenon. During the research stages where data from Permian fields were analyzed to develop this new design of gas separator, the engineering team found three main challenges in downhole gas separation. First, the wells were converted from Electrical Submersible Pump (ESP) to Rod Pumps earlier, forcing the downhole gas separators to handle more production. Second, the small production casing size usually is 5.5" casing, which significantly reduces the annulus area, which is vital to get an effective gas separation efficiency, and third the gas slugging behavior, which in high proportion can lead to a gas lock-in sucker rod pump system. A packer-type gas separator was designed, built, and tested in multiple wells following the requirements and limitations. This gas separator has an outlet section of 1.89" O.D., which means the design maximizes the gas separation area where it really matters at the fluid outlet point. The revolutionary fluid exit slots design creates a linear flow path allowing gas to separate and flow upward the casing annulus in a natural way. Additionally, a valve below the cup packer was included to eliminate surging. This valve prevents surging by holding the fluid in the vertical section, thus avoiding backflow when the gas slug leaves liquids behind. A calculator was developed to estimate the gas separation efficiency downhole and compare the gas separation efficiency among different gas separators to evaluate the new design. After the implementation of this design in 5 wells, the results confirmed the high gas separation efficiency obtained with this new gas separator configuration. The novelty of this gas separator design is the outlet section that takes advantage of the gravity force to increase the gas separation efficiency without limiting the tensile strength of the Bottom Hole Assembly (BHA).
- North America > United States > Texas > Permian Basin > Yeso Formation (0.99)
- North America > United States > Texas > Permian Basin > Yates Formation (0.99)
- North America > United States > Texas > Permian Basin > Wolfcamp Formation (0.99)
- (22 more...)
Abstract Downhole gas separators are often the most inefficient part of a sucker rod pump system. This paper presents laboratory data on the performance of five different gas separator designs. Only continuous flow was studied. Field data is presented on one of the designs. The field data indicates that success or failure of the gas separator is dependent upon the fluids and wellbore pressures as well as the mechanical design of the gas separator. Successful and unsuccessful examples of gas separator performance in the field are shown along with field fluid data properties. Videos will be shown at the presentation of the continuous and intermittent flow of water and air through the transparent gas separators placed in transparent casing. While the study is not completed, this is the first of hopefully several papers that will present the results of this investigation. Introduction Patterson studied some different down-hole gas separation designs for coal bed methane operations in Wyoming. In these designs the inlet to the gas separators were smaller than normally used and along with some baffles, thought to allow gas to vent from inside the gas separator, obtained good gas separation in the field installation. While field installations provide the ultimate validation of gas separator performance, it is extremely difficult to isolate the influence of each design parameter. It was these installations which prompted the laboratory study of the gas separator geometry to understand if the "rules-of-thumb" used by the industry for gas separator design were valid. One of the most common sources of inefficiency in oil well pumping installations (rod pumps, ESPs of PC pumps alike) is gas interference, which prevents the pump from delivering liquid at the design rate. Although this is a well known effect, there seems to be limited understanding of the mechanisms that control gas interference and this often results in the use of remedies, such as installing downhole gas separators, that are ineffective or even detrimental to the pumping system performance. The objectives of this paper are to give a clearer insight on the mechanisms of gas interference in pumping wells and to present the results of recent laboratory and field studies on the flow characteristics and performance of some downhole gas separators. In a pumping installation, one of the principal functions of the wellbore is to operate as a two-phase (gas-liquid) separator so that the pump (which is designed to pump liquid) can operate efficiently. Although this concept appears to be obvious, it seems to be totally ignored by most operators when they design completions and install hardware (gas anchors and the like) to combat the effects of gas interference. In these applications, the separation of gas from liquid is achieved through GRAVITY separation without the introduction of other mechanisms (centrifugal forces, nozzles, etc.). Thus, the difference in density between the gas and liquid is the main driving force to be used for separation. This also implies that forces that oppose the effect of gravity, such as viscous drag caused by high fluid velocity and turbulence, will be detrimental to the separation process.
Abstract Downhole gas separators are often the most inefficient part of a sucker rod pump system.This paper presents laboratory data on the performance of five different gas separator designs. Only continuous flow was studied. Field data is presented on two of the designs.The field data indicates that success or failure of the gas separator is dependent upon the fluids and wellbore pressures as well as the mechanical design of the gas separator.Successful and unsuccessful examples of gas separator performance in the field are shown along with field fluid data properties. Introduction Patterson[1] studied some different down-hole gas separation designs for coal bed methane operations in Wyoming.In these designs the inlet to the gas separators were smaller than normally used and along with some baffles, thought to allow gas to vent from inside the gas separator, obtained good gas separation in the field installation. While field installations provide the ultimate validation of gas separator performance, it is extremely difficult to isolate the influence of each design parameter. It was these installations which prompted the laboratory study of the gas separator geometry to understand if the "rules-of-thumb" used by the industry for gas separator design were valid. One of the most common sources of inefficiency in oil well pumping installations (rod pumps, ESPs of PC pumps alike) is gas interference, which prevents the pump from delivering liquid at the design rate. Although this is a well known effect, there seems to be limited understanding of the mechanisms that control gas interference and this often results in the use of remedies, such as installing downhole gas separators, that are ineffective or even detrimental to the pumping system performance. The objectives of this paper are to give a clearer insight on the mechanisms of gas interference in pumping wells and to present the results of recent laboratory and field studies on the flow characteristics and performance of some downhole gas separators. In a pumping installation, one of the principal functions of the wellbore is to operate as a two-phase (gas-liquid) separator so that the pump (which is designed to pump liquid) can operate efficiently. Although this concept appears to be obvious, it seems to be totally ignored by most operators when they design completions and install hardware (gas anchors and the like) to combat the effects of gas interference. In these applications, the separation of gas from liquid is achieved through GRAVITY separation without the introduction of other mechanisms (centrifugal forces, nozzles, etc.). Thus, the difference in density between the gas and liquid is the main driving force to be used for separation. This also implies that forces that oppose the effect of gravity, such as viscous drag caused by high fluid velocity and turbulence, will be detrimental to the separation process. Thus, high velocity of liquid or gas should be avoided if possible. The Pumping Wellbore as an Efficient Gas-Liquid Separator The preferred pumping installation for maximum pump efficiency requires installing the pump intake BELOW the lowest point of fluid entry into the wellbore and requires having an open casing-tubing annulus from the bottom to the wellhead. This configuration is shown in Figure 1A. Gas and liquid enter the wellbore through the perforations and liquid flows to the bottom of the well under the action of gravity. The lighter gas bubbles rise through the liquid forming a gaseous liquid column, from the bottom of the perforated interval to the fluid level, then gas flows through the casing-tubing annulus to the wellhead where it exits to the flow line. Practically 100% liquid accumulates at the bottom of the well and enters the pump intake to be discharged by the pump into the tubing. This completion is similar to the surface facility vertical two-phase separator shown in Figure 1B. To be equivalent both the x-sectional area for flow diameter to length ratios would have to be the same. The gas-liquid mixture enters the vessel about two-thirds up the vessel wall. The gas outlet is at the top of the vessel; Liquid falls to the bottom and accumulates in the "quieting chamber" of the vessel where it flows to the pump intake through the liquid outlet.Proper operation of the separator requires that the liquid retention time be sufficient for most of the gas bubbles to rise to the gas/liquid interface and that the gas velocity be low enough for most of the liquid droplets to fall to the gas-liquid interface. These are the two criteria used for correctly sizing the separator to meet the flowing requirements. The unusual characteristics of this "equivalent separator" are that:It would have to be built with 4 to 7 inch diameter pipe It would be at least 30 feet tall It would not have liquid level controls The capacity of a 2-phase separator is defined in terms of liquid and gas capacity as a function of operating pressure and gas and liquid densities
Abstract The performance prediction of a Rotary Gas Separator (RGS) is very important for ESP systems applications. The pump performance is severely affected when it handles high Gas Void Fraction (GVF) at its intake. The function of the RGS is to separate both liquid and gaseous phases, and to expel the gas through a crossover section to the annular area between casing and tubing. Typical designs use separation efficiency values based on an empirical standpoint of view. Also, the literature references regarding an important parameter like the inducer head is very scarce. The performance analysis of a RGS (540 series separator), under two-phase flow conditions, has been conducted using 3D-CFD simulation tools (CFX 5.6). Water-air mixtures were used as working fluid and the mixture GVF was varied from 10% up to 30%. The results shows that the RGS separates efficiently the phases, but the inducer head is insufficient to overcome the friction losses in the crossover and the liquid column static pressure in the annular space. As a consequence, a new inducer design is necessary to create a higher head value to push the gaseous phase out of the RGS and not to be dragged by the liquid phase. The simulation could be an alternative tool for selecting the depth of the downhole equipment as a function of the liquid level. This could help the designer to properly obtain the minimum submergence of the equipment that satisfy the phases separation and gas expulsion of the RGS, getting a lower GVF at the PIP. Introduction Electrical Submersible Pump (ESP) is one of the artificial lift methods commonly used, which is a multiple stage centrifugal pump. When a centrifugal pump handles liquid with free gas at the intake it experiments performance degradation. Depending on free gas amount, the consequences can vary from light pump performance degradation up to pump gas locking. Typical solutions to reduce the free gas amount at the pump intake are the installation of gas separators or gas handling devices (special geometries). The Rotary Gas Separators (RGS), has been traditionally used, but its performance under two-phase flow is still not well understood. The major efforts to analyze RGS's performance has been done by several authors1–4, through experimental works and theoretical models. The separation phenomenon has two domains; natural gas separation in the annular space and gas separation process inside the separator device. The separation efficiency of the RGS depends on the centrifugal force and the inducer head. The last parameter is very important to overcome the crossover losses and annulus' backpressure producing the gas expelling to the annular space. The objective of the present work is to study the inducer performance (separation phases process and head developed) using 3D two-phase numerical flow simulation. A commercial code was used (CFX 5.6) to simulate the two-phase flow inside of RGS inducer. Theoretical Background In this section, the basic definitions and some RGS components will be discussed. Inducers. An inducer is a low-head axial flow impeller with few blades, basically used to provide little booster pressure to a conventional impeller. The purpose of the inducers in rotary separators is to supply the centrifugal force necessary for phase's segregation and the required gas energy to overcome the crossover losses and annulus' backpressure. Intake Section. In the design of ESP installations, one key factor is the free gas amount at the intake. This parameter sets the criteria to choose the pump "intake section" completion among: simple intake, gas separator intake or advance devices for handling the gas. Gas separators are devices employed to expel the gas into the annulus reducing the gas handled amount by the pump. Depending on the separation concept, there are two kinds of equipment: a) The reverse flow or static separators (gas anchor) based on pressure drops and changes on flow direction (momentum) whose efficiency is reduced by the gas dragged by the liquid and b) The rotary separators' based on the phase's segregation induced by the huge centrifugal forces.
- South America (0.94)
- North America > United States (0.69)
- Research Report > New Finding (0.34)
- Research Report > Experimental Study (0.34)