advances in environmental biology 9/877-882.pdf878 hamzeh ghorbani and jamshid moghadasi, 2014...

Advances in Environmental Biology, 8(17) Special 2014, Pages: 877-882

AENSI Journals

Advances in Environmental Biology ISSN-1995-0756 EISSN-1998-1066

Journal home page: http://www.aensiweb.com/AEB/

Corresponding Author: Jamshid Moghadasi, Department of Petroleum Engineering, Omidiyeh Branch, Islamic Azad University, Omidiyeh, Iran E-mail: [email protected]

“Development of a New Comprehensive Model for Choke Performance Correlation

in Iranian Oil Wells”

Hamzeh Ghorbani and Jamshid Moghadasi Department of Petroleum Engineering, Omidiyeh Branch, Islamic Azad University, Omidiyeh, Iran A R T I C L E I N F O A B S T R A C T Article history: Received 25 June 2014 Received in revised form 8 July 2014 Accepted 25 November 2014 Available online 16 December 2014 Keywords:

Multiphase flow occurs in all producing oil and Gas/Condensate wells. There is some Choke in flowing well to modulate the flowing rate. Some reasons are proposed for this modulating action: (1) to prevent enough back pressure to stop sand entry, (2) to safe surface equipment from high pressure, (3) to protect gas or water coning and (4) to keeping the reservoir at the optimum flow rate. Many mathematical models which correlate the rate of multiple phase flow through an orifice (choke) exist. The models offer empirical correlations which are based upon laboratory and field data. This article proposed a new empirical correlation pattern for under critical flow based on 76 production test points analyses collected for 10 wells in south Iran. The average error of sub-critical flow is about1% over entire range of oil production rates of 7000-28000 ( ), pressures of 100-1000 (psi), choke size of 42-98 (1/64th-inch) and gas oil ratios of 100-220 ( ). In this study, we use the data GLR . Because of this condition was lower than the value of the production rate has not trustworthy range.

© 2014 AENSI Publisher All rights reserved. To Cite This Article: Hamzeh Ghorbani and Jamshid Moghadasi, “Development of a New Comprehensive Model for Choke Performance Correlation in Iranian Oil Wells”. Adv. Environ. Biol., 8(17), 877-882, 2014

INTRODUCTION

Choke in a producing well is responsible for controlling the production. There are some tools to control the flow rate. These tools are used for the following purposes [12].To prevent enough back pressure to stop sand entry. A) To safe surface equipment from high pressure. B) To protect gas or water coning. C) To keeping the reservoir at the optimum flow rate. Several correlations have been proposed for explaining critical and subcritical multiphase flow through wellhead chokes [2]. These correlations are based on limited ranges of flow variables. The validity of these correlations is limited, based on quality and range of data. Gilbert (1954) developed the most popular correlation. When the upstream pressure of the choke is at least 70% higher than the downstream pressure or when the ratio of downstream pressure to upstream pressure is equal to 0.588 [7]. However, rather than Gilbert’s equation in the literature other researchers introduce different correlations. There are two conditions for flow through the wellhead choke. Table 1: Equation coefficient for different correlations and their accuracy (General form Eq.1).

Correlation Empirical Coefficient QL

A B C Average Mean Error % Min Average Error % This Study 0.8167 -0.627 -1.621 -0.872 0.226

Gilbert 10.0 0.546 1.890 -63.81 -57.47 Ros 17.4 2.00 0.500 60.01 -51.57

Baxcendell 9.56 0.546 1.930 52.64 31.48 Achong 3.82 0.650 1.880 41.45 21.22 Liaghat 315 0.560 -1.79 -66.08 61.38

878 Hamzeh Ghorbani and Jamshid Moghadasi, 2014 Advances in Environmental Biology, 8(17) Special 2014, Pages: 877-882

Table 2: Range of data used for the correlations. Flow Rate GLR Choke Size Wellhead Pressure

(bbl/day) (STB/Day) (SCF/STB) (1/64) in (Psi) 7000-28000 100-220 42-98 100-1000

In this article, the critical flow condition refers to situation in which the flow rate reaches a maximum amount without regard to the pressure difference to downstream and upstream of the choke. In return, the flow rate in sub-Critical flow depends on pressure difference across the choke and changes in the downstream pressure causes the change upstream pressure. Empirical correlations are applied for critical flow condition. Backgrounds: For the first time, the theory of multiphase fluid flow in choke was proposed by Tangren et al. in 1949. This theory can be useful when the phase is continuous and the gas liquid ratio is lower than one. In1954, Gilbert proposed an experimental theory by using 268 test data to choke measures between 6.64 to 18.64. Gilbert’s equations show the bellow correlation:

( )64

( )

CP DwhQ

L BA GLR=

Where: QL= liquid production rate (bbl/day). GLR= gas-liquid ratio (SCF/STB). Pwh= well (or tubing) head pressure (psig). D64=bean size (1.64) inch. A, B, C= empirical constant. The second experimental relation was introducted by Baxcendell in 1957. In 1960, Ros proposed his work based on Tangren theory for the state in which the gas is continuous. Achong proposed the third experimental relation in 1960. After Achong, in 1963, Poettmann and beck converted Ros model to the field unit and introduced a new model. In 1969, Omana carried out some experiments by using natural gas and water system and they obtained a relation and the choke range of 6.64 to 14.64 (inch) and productive maximum rate was 800 galon per day. In 1972, fortunate also introduced two relations for sub-critical and critical flows. He used Guzov and Medivedive log for critical flow. In 1975, Ashford and Pierce proposed a relation the particular heat has been used which the mentioned parameter is not measured in field experiments and there is no relation to estimate that. In 1980, pilevary proposed another model. Sachadov proposed a relation in 1986 which needed a particular heat. In 1990, Osman and Dakla obtained a relation for condensate gas. In 2007 Alrema and Bizanti introduced a relation for one of the KWT fields and Ansfran and Kalkar proposed a theoretical relation. Developments of new correlation and discussion: Levenberg-Marquardt algorithm:

In this study, Levenberg-Marquardt algorithm is used to find the minimum of a multi-variable nonlinear

function which is used to solve the square minimum problem.

Newton algorithm and gradient descent method LMA is more resistant than GNA, but it is slower than

GNA. P-parameter is used in GNA and you can find P-parameter and its details in the present study [11].

RESULTS AND DISCUSSIONS

76 production test data point were collected for 10 wells, including the liquid flow rate, gas-liquid ratio, choke Size and wellhead pressure liedare within the reign 7000-28000 (STB/day), 100-220(SCF/STB), 42-98(1/64th-inch) and 100-1000(Psi), respectively. Range of the data used is tabulated in Table2.

The first proposed correlation, a modified Gilbert equation based on regression analysis for the field is: ( )64

( )

CP DwhQL BA GLR

= , A=0.8167, B=0.627, C=1.621 (2)

One type of errors were calculated using the following two equations:

% 100S S

Meassured CalculatrdMinAveragePercentErrorS

Meassured

−= ×

100% ( )1

S Sn Meassured CalculatrdAverageMeanPercentError n Si Meassured

−= × ∑

=


Where:

S= amount

The comparison of the performance of correlation i.e. measured vs. calculated production data, i.e. Gilbert, Ros, Baxcendell, Achong, Liaghat and this study are shown in Fig. 1a and Fig. 1b respectively. Figures 2a and 2b through 4a and 4b illustrate the statistical results of wellhead pressure, produced gas/oil ratio and choke size on the performance of the aforementioned correlations. Conclusions: Using the statistical results obtained in this work the following conclusions have been reached. 1. The use of 76 production test data point were collected for 10 wells in Southern Iranian oilfield led to the development of equation by the use of Least square technique are shown below:

1.621( )640.6270.8167( )

P DwhQL GLR

=

The range of flow rate, pressure, choke size, gas/oil ratio is tabulated in Table 2. 2. Since that for choke relations is the case study, while or if the data field are available for each field, can be a quire own unique the stream relation field, it cases accuracy of the calculations. 3. The result of the study shows that this study calculates production rates with an Average error % below 1%��One can also conclude that equation and Achong equation are placed second and respectively.

4. In this study, we use the data GLR . Because of this condition was lower than the value of the

production rate has not trustworthy range. 5. After determining the coefficients of the equation and generated by the pressure, choke size and gas oil ratio

can be estimated the gas rate. Appendix A Nomenclature

A Proportionality constant

B Gas-oil ratio exponent

C Bean or choke size exponent

QL Liquid flow rate, STB/day

Pwh Well head pressure, psig

D64 Choke Size, (1/64-inch)

GLR Producing gas-liquid ratio at standard

S Amount

STB Stock tank barrel

SCF Standard cubic foot

REFERENCES

[1] Achong, I., 1961. Revised Bean Performance Formula for Lake Maracaibo Wells. Internal co. report, Shell

Oil Co., Houston, TX. [2] Al-Attar, H.H., 2009. New Correlations for Critical and Subcritical Two-phase Flow Through Surface

Chocks in High-Rate Oil Wells. SPE 120788. [3] Al-Towailib, A.I., M.A. Al-Marhoun, 1992. New Correlation for Two-phase Flow through Chokes. M.S.

Thesis, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia. [4] Baxendell, P.B., 1958. Producing Wells on Casing Flow – An Analysis of Flowing Pressure Gradients,

AIME, 213: 202–207. [5] Economides, M.J., A.D. Hill., C. Ehlig-Economides, 1993. Petroleum Production Systems. Prentice Hall

PTR, New Jersey, pp: 229. [6] Engineering Data Book, 13th edition, Vol.1, Chapter 3, Gas Processors Suppliers Association, 2012. [7] Ghareeb, M., A. Shedid, 2007. A New Correlation for Calculating Wellhead Production Considering

Influence of Temperature. GOR and Water-Cut for Artificially Lifted Wells, IPTC 11101. [8] Gilbert, W.E., 1954. Flowing and Gas-Lift Well Performance. Dril. And Prod. Prac. API, 143: 127–154. [9] Jin, L., A.K. Wojtanowicz, 2010. Coning Control and Recovery Improvement Using in-Situ Water

Drainage/Injection in Bottom–Water-Drive Reservoir. SPE 129663.


[10] Safar Beiranvand., M., P. Mohammad moradi, B. Amin shahidy, B. Fazelabdolabadi, S. Aghahoseini, 2012. New multiphase choke correlations for a high flow rate Iranian oil field. Mechanical Sciences,20 May.

[11] Alrumah., M., M. Bizanti, 2007. New Choke Correlations For Sabrina Field. Kuwait, SPE 105103. [12] Mesallati, A., M. Biznati, N. Mansouri, 2000. Multiphase-Flow choke correlations for Offshore Bouri Oil

field. International Gas Union 21st World Gas Conference, Nice, France. [13] Ros, N.C.J., 1961. An Analysis of Critical Simultaneous Gas/Liquid Flow through a Restriction and Its

Application toFlow metering. Applied Science Research, 9: 374–388. [14] Sachdev, A.R., Z. Schmidt, J.P. Brill, 1986. Two-phase Flow through Chokes. Paper SPE 15657 presented

at the 1986 SPE Annual Technical Conference and Exhibition, New Orleans, Louisiana, 5-8 October. Appendix B Graphs

Fig 1a:

Fig 1b:


Fig 2a:

Fig 2b:

Fig 3a:


Fig 3b:

Fig 4a:

Fig 4a:

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