Multiphase pumping has consolidated itself as the state of the art technology in crude oil transport for declining and marginal fields. Several types of pumps have been applied or developed for such service, opening a new research trend worldwide. In this research we studied the progressive cavity pump performance with two-phase flow. Our aim was to obtain the pressure and temperature profiles along the pump's stator, and to observe its behavior under different sets of variables such as gas void fraction, rotational speed and Ap. The knowledge that can be acquired will be useful to estimate how flow conditions can be affecting the pump's life and the smoothness of the pump performance. The results showed that for single-phase flow at low Ap the maximum pressure is not located at the pump outlet as it would be expected. The pressure distribution in the pump with two phase flow is completely different to the latter case, being found that within the pressure range of the experiment the cavities are kept sealed almost along the whole pump. For any point of operation the maximum temperature is found in the intermediate stages.
Multiphase production systems are being considered as a development option for many fields on a worldwide basis. Engineers are faced with the challenge of selecting the best candidates to take full advantage of this novel technology. A review of the literature reveals that no guidelines have yet been published regarding this issue. This paper utilizes classical reservoir engineering methods to model the interaction of a surface installed multiphase pump with the reservoir and tubing. A derivative analysis of the backpressure equation is used to show the difference in incremental production among wells with different backpressure coefficients and exponents. A method was developed which combines well deliverability and decline data to forecast the impact of a multiphase pump on reserves, i.e. ultimate recovery. The results of this study indicate that:wells exhibiting a low wellhead backpressure coefficient (n) make poor candidates for multiphase pumping;plotting the derivative of the wellhead backpressure equation provides a means of defining a threshold, which must be reached before a multiphase pump, would provide value;liquid loaded wells may yield the best response to a surface installed multiphase pump; and,reduction of the backpressure on a well, through use of a multiphase pump, acts to increase the ultimate recovery for a well or field. Introduction Multiphase pumping has been shown to provide value in a number of different operating environments. These include heavy oil production in Venezuela,1,2,3 California4 and Italy,5 light oil production in Canada,6 Indonesia,7 and Trinidad,8 as well as gas condensate fields9 and subsea production.10 A summary of the various multiphase pumping technologies as well as a discussion of their worldwide applications was presented by Scott11 and Scott and Martin.12 All of these methods are installed on the surface to boost the pressure of the fluids produced from the wellhead. This study does not consider a particular multiphase pump technology, but rather the general method of using a multiphase pump to decrease wellhead pressure. The goal of this paper is to define methods that can be invoked to identify the best candidate wells for a reduction in wellhead pressure. This paper utilizes classical reservoir engineering methods to model the interaction of a surface installed multiphase pump with the reservoir and tubing. First, bottomhole reservoir deliverability is analyzed to identify which reservoirs will best respond to a reduction in bottomhole pressure. The derivative of the backpressure equation is used to show the difference in incremental production associated with a reduction in wellhead flowing pressure among wells with different backpressure coefficients and exponents. Next, the expression for oil well deliverability at the wellhead developed by Thrasher, Fetkovich and Scott (1995)13 is utilized to consider the effects of tubing on candidate wells. The impact of a lower wellhead pressure on liquid loaded wells and tubing limited wells is discussed. Also, a simple economic model is proposed for comparison of the costs and benefits of a multiphase pumping project. Finally, the impact of backpressure on ultimate recovery is considered. The work of Fetkovich et al (1996)14 develops the relationship between the wellhead backpressure exponent and the decline type/ultimate recovery of the reservoir. Using this approach, a method was developed which combines well deliverability and decline data to forecast the impact of a multiphase pump on reserves. System Analysis - Steady-State The response of a well to a reduction in wellhead pressure, through use of a multiphase pump, depends on the overall production system. This includes the reservoir, formation completion and tubulars. The steady-state response of the reservoir and completion will first be considered through bottomhole analysis.
Lamb carcasses (n = 94) from five packing plants, selected to vary in weight class and fat thickness, were used to determine retail yield and labor requirements of wholesale lamb fabrication. Carcasses were allotted randomly according to weight class to be fabricated as whole carcasses (n = 20), three-piece boxes (n = 22), or subprimals (n = 52). Processing times (seconds) were recorded and wholesale and retail weights (kilograms) were obtained to calculate retail yield. Subprimals were fabricated into bone-in retail cuts or boneless or semi-boneless retail cuts. Retail yield for subprimal lamb legs decreased from 85.3 +/- .6% for bone-in to 68.0 +/- .7% for a completely boneless retail product. Correspondingly, processing times increased from 126.1 +/- 5.4 s to 542.0 +/- 19.2 s for bone-in and boneless legs, respectively. For all subprimals, retail yield percentage tended to decrease and total processing time increase as cuts were fabricated to boneless or semi-boneless end points compared with a bone-in end point. Percentage retail yield did not differ (P > .05) among whole carcass, three-piece box, and subprimal marketing methods. Total processing time was shorter for subprimals (P < .05) than for the other two marketing methods.
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