A New Correlation for Calculating Wellhead Production Considering Influences of Temperature, GOR, and Water-Cut for Artificially Lifted Wells
Authors: Ghareeb Mohamed , Elgaghah Shedid 
Published: February 2016

Several classical wellhead production correlations have been developed and widely used all over the world for naturally flowing wells. For artificially flowing wells, many important well and fluid parameters are ignored in these correlations. This results in erroneous results and inaccurate predictions when these correlations are applied. These current correlations are mainly function of tubing head pressure, bean size (which has almost no effect for artificially flowing wells), and gas-liquid ratio only.

The man objective of this study is to ovecome the limitations of these correlations for artificially flowing wells by development a new correlation capable to predict accurately the wellhead flow production. The new correlation was developed using a set of 1,750 data points from 352 producing wells in Egypt. The newly-developed correlation includes several parameters of tubing size, wellhead and bottom-hole temperatures, producing gas-oil ratio, pay zone depth, and water cut. A sensitivity analysis using the newly-developed correlation about the influences of involved well and reservoir parameters, is carried out.

The results indicated that the newly-developed correlation is capable to predict the wellhead production rate accurately. Noteworthy, the variation of producing depth, tubing size and wellhead temperature has real impact on production rate while variation in bottom-hole temperature, water-cut and gas-oil ratio has relatively smaller effect on well production rate.

The enhanced prediction of production rate using the new correlation is attributed to its consideration to many other parameters, which were ignored before in Gilbert and other's correlations; such as tubing size, wellhead temperatures, and pay zone depth.

1. Introduction and Literature Review

The separator and multiphase meters have been considered and used to determine the oil well production. This has been considered as the most accurate method for calculating the oil and gas flow rates. However, these current methods are rather expensive and time consuming to be achieved. Therefore, it is usually desired to have quick and accurate evaluation of well performance considering wellhead parameters, especially pressure and temperature. Good utilization of pressure and temperatures parameters of producing wells reveals excellent and reliable information about well behavior and can help to make required remedial action(s) in required suitable time.

For naturally flowing wells, bean performance correlation is the most widely used to monitor well performance. Most current correlations (Gilbert, 1954; Ros, 1960; Ashong, 1961; Asford, 1973; Secen, 1976; Abdul-Majeed, 1986) for two-phase flow across chocks are valid only for critical flow across the choke. The literature presented good correlations for single phase flow of either liquid or gas. However, reliable correlations for two-phase are limited and for multiphase are rare and scarce. This is especially true for flow in the sub-sonic flow region (i.e., flow velocities smaller than that of sound.

The majority of current correlations for multiphase flow are valid only for critical flow condition. The most popular correlation was developed by Gilbert (1954) but it is valid for critical flow occurring when the upstream pressure of the choke is at least 70 % higher than the downstream pressure or when the ratio of down stream pressure to upstream pressure is equal to 0.588. In general, the literature (Abdul-Majeed, 1986; Al-Attar and Abdul-Majeed, 1988) reveals that keeping the ratio of downstream pressure to upstream pressure in the range from 0.50 to 0.60 secures the critical flow condition of the choke.