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Article
Effect of Pressure and Temperature Change on Undersaturated Oil Viscosity

Author: Mohammed M. Daway
Journal: Journal of Petroleum Research & Studies مجلة البحوث والدراسات النفطية ISSN: 22205381 Year: 2012 Volume: 261 Issue: 5th Pages: 152-161
Publisher: Ministry of Oil وزارة النفط

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Abstract

A study has been done based on data received from one of the southern Iraqi's oil fields, consists of eighty eight experimental points of oil viscosity at known pressure and temperature above the bubble point pressure.Fourteen formulas assumed to define the effect of pressure and temperature change on undersaturated oil viscosity. Every formula gives a value of viscosity at any temperature and pressure (above bubble point) depending on a known value ofviscosity at known pressure and temperature. Depending on the least squares method, the constants of these formulas are calculated.A formula appeared to have the minimum average absolute error (4.8 %) with a value of correlation coefficient equal to (0.8996) is selected to be the best formula adopted in this study. The most proper formula has been compared with two correlations (Khan's correlation and Vasquez and Beggs correlation) and it appeared to be better than the both correlations.

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Article
Proposed Correlation for Gas solubility at and below Bubble Point Pressure
صيغة مقترحة لحساب ذوبانية الغاز عند وتحت ضغط نقطة الفقاعة

Author: Mohammed M. Daway
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2014 Volume: 32 Issue: 6 Part (A) Engineering Pages: 1497-1505
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

A study has been done to get an accurate correlation for solution gas-oil ratio (gas solubility). Two hundred and nine measured values from an Iraqi oil field have been used in this study.Many formulas are tested to get the best correlation for gas solubility. Every formula predicts the value of gas-oil ratio at any given pressure, temperature, oil density and gas specific gravity. Based on the nonlinear regression analysis, the constants of these formulas are determined.The formula with the minimum average absolute error among the assumed (reported an absolute average error of 4.97 % and a standard deviation of 453) is selected to be the proposed correlation for this study.The accuracy of the proposed correlation is assessed through a statistical test and compared with those achieved for some published correlations. This test shows that the proposed correlation has the best fitting with the experimental data. Cross plot technique is also applied to check the performance of the correlation which gave the same index of the statistical criterion method.Another method has been used to ensure the accuracy of the proposed correlation, in which a sample of external data (which is not used to develop the correlation) is tested. The results show the same index of the other methods

تم إجراء دراسة للحصول على علاقة دقيقة لذوبانية الغاز (نسبة الغاز المذاب إلى النفط). مئتان وتسع قيم مقاسة من أحد الحقول العراقية تم إستخدامها في هذه الدراسة.تم إفتراض عدد من الصيغ لإيجاد أفضل علاقة لذوبانية الغاز، كل صيغة تعطي قيمة لذوبانية الغاز عند قيم معلومة للضغط ودرجة الحرارة وكثافة النفط والغاز. إعتماداً على طريقة تحليلات التراجع الخطية، تم حساب ثوابت الصيغ المقترحة.الصيغة التي حصلت على أقل نسبة خطأ بين الصيغ المفترضة (4.97 %) وسجلت إنحراف معياري مقداره (453) تم إختيارها لتكون الصيغة المتبناة (أو المقترحة) في هذه الدراسة.تم تقييم دقة الصيغة المقترحة عن طريق إختبارات إحصائية، حيث تم إجراء مقارنة لهذه الصيغة مع بعض الصيغ المنشورة سابقاً. وقد أظهرت هذه الإختبارات بأن العلاقة المقترحة أفضل من بقية الصيغ نسبة للبيانات المتوفرة. طريقة الرسم إستخدمت كذلك للتحقق من فعالية العلاقة، وقد أعطت الطريقة نفس الإنطباع الذي أعطته الطريقة السابقة.


Article
Pressure Changes in Pipe Transporting Mixture of Iraqi Crude Oils (Gathering System)

Authors: Maha R. Abdul-Ameer --- Mohammed M. Daway
Journal: Journal of Petroleum Research & Studies مجلة البحوث والدراسات النفطية ISSN: 22205381 Year: 2013 Volume: 191 Issue: 9th Pages: 90-126
Publisher: Ministry of Oil وزارة النفط

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Abstract

A study has been done to represent the pressure changes along gathering system in pipelines transporting Iraqi's crude oils; the study is divided into four parts. The first part represents the calculations of pressure drop in pipelines transporting petroleum fluid from the well head to a gathering point. In this part, there is a two-phase flow (gas and liquid). The calculations of pressure change in this part depends upon determination of some properties such as liquid and gas density, liquid and gas viscosity, liquid hold up and friction factor.Determining the liquid hold up and then pressure drop are achieved using two methods, the first method is modified Beggs and Brill correlation, depending on three assumed flow patterns. The second is Aziz et al. correlation, depending on three flow patterns also but are different to that of modified Beggs and Brill. While a method of Colebrook used in determination of two-phase friction factor. The results of two-phase flow calculations show that modified Beggs and Brill correlation (having error of 0.26%) better than Aziz et al. correlation (having error of 0.55%).In the second part there are calculations of pressure change in liquid flow in a pipeline from the gathering point to the first stage of separators. In this part Colebrook correlation is used to determine the friction factor, Brill and Mukherjee method is used for calculation of pressure change.Mukherjee and Brill method gave good results with respect to the pressure drop of flow in the axial pipeline after the gathering point of the actual field data. The third part deals with the networking in pipelines, types of gathering systems presented and discussed, the calculations of pressure change in a simple gathering system is studied. The fourth part discusses optimization techniques; Constrained Rosenbrock is used to find optimum pressure which gives favorable oil properties. They have been achieved with some assumptions; they are:1.Minimum Produced gas oil ratio.2.Minimum formation volume factor.3.Maximum API gravity.Finally, two computer programs are developed. Each program performs all the calculations of the four parts. The first program is developed using FORTRAN language, while the second is developed using Visual Basic language.

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