12 Feb, 2015

Why CO2 Flashing from Water is Important for CO2 EOR Flood Separators and Tanks

In this Tip of the Month (TOTM) we will discuss how to determine CO2 solubility and flashing issues in water at pressures and temperatures commonly associated with gathering systems and production facilities. This is mainly important for CO2 Enhanced Oil Recovery (EOR) floods as the CO2 concentration is high and the initial separation is at higher pressures than is common in non-CO2 EOR oilfields. These two conditions result in significant dissolving of CO2 into the produced water with resultant flash gas from downstream Free Water Knockouts (FWKO), treaters, and tanks. In mature CO2 EOR floods with Water-Alternating-Gas (WAG) injection schemes, it is likely that most of the flash gas in the downstream separations will be from the produced water. While this TOTM is significant mainly for CO2 EOR floods, the following analysis is general in nature; it would apply to other situations involving CO2 solubility in water issues. This analysis assumes that there is no H2S. H2S would have somewhat higher solubility than CO2 which would force more gas to flash from the FWKO and tanks. Higher H2S than about 5% would begin to appreciably increase the solubility of H2S into water.

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21 Jan, 2015

Variation of Crude Oil Properties with Temperature in a Gathering Line

In the October and November 2014 Tips of the Month (TOTM), we demonstrated that Gas-Oil-Ratio (GOR) has a large impact on the capacity of crude oil gathering lines. If GOR is less than the saturation solution gas, the increase in GOR reduces the viscosity and density of crude oil which causes the pressure drop to decrease. However, if the GOR exceeds the saturation solution gas the system becomes two phase and pressure drop increases. The solution gas is a function of temperature, pressure, gas and liquid compositions. In this TOTM, we will study the impact of temperature on the crude oil properties in the gathering systems for the case presented in the November 2014 TOTM. Specifically, the variation of the crude oil relative density and viscosity with the temperature will be studied. Finally, the impact of temperature on the oil and gas velocity and pressure drop along a gathering line for nominal pressure of 6900 kPag (1000 psig) and nominal pipe size of 101.6 mm (4 inches) will be demonstrated using a multiphase rigorous method from a commercial simulator. The calculated properties, oil and gas velocities and pressure drops are presented in graphical format as a function of the oil stock tank volume flow rate, solution gas, Rs, and temperature.

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4 Nov, 2014

Impact of Solution Gas on Crude Oil Properties in a Gathering Line

In the October 2014 Tip of the Month (TOTM), we demonstrated that Gas-Oil-Ratio (GOR) has a large impact on the capacity of crude oil gathering lines. In general as GOR increased the pressure drop increased which lowered the line capacity. In addition, at high pressures and low GOR, pressure drop was lower than the pressure drop for dead oil (solution gas is zero) because the viscosity of live oil is lower than viscosity of dead oil. This effect was bigger for the smaller line diameter. In this TOTM, we will study the impact of solution gas (Rs) on the crude oil properties in the gathering systems for one of the cases presented in the October 2014 TOTM. Specifically, the variation of the crude oil relative density and viscosity with the solution gas (Rs) will be studied. Finally, the impact of solution gas (Rs) on the oil and gas velocity and pressure drop along a gathering line for nominal pressure of 6900 kPag (1000 psig) and nominal pipe size of 101.6 mm (4 inches) will be demonstrated using multiphase rigorous method from a commercial simulator. The calculated properties, oil and gas velocities and pressure drops are presented in graphical format as a function of the oil stock tank volume flow rate and solution gas, Rs

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3 Sep, 2014

Lean Sweet Natural Gas Water Content Correlation

In the October, November, December 2007 and February 2014 Tips of the Month (TOTM), we studied in detail the water phase behaviors of sweet and sour natural gases and acid gas systems. We also evaluated the accuracy of different methods for estimating the water content of sour natural gas and acid gas systems. The water vapor content of natural gases in equilibrium with water is commonly estimated from Figure 6.1 of Campbell book or Figure 20.4 of Gas Processors and Suppliers Association (GPSA), including corrections for the molecular weight (relative density) of gas and salinity of water. In this article, we will present two new correlations for estimating the water content of lean and sweet natural gases. The performance of the proposed correlations is compared with the rigorous simulation and shortcut method software and other correlations.

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4 Aug, 2014

The Importance of Leadership in Process Safety Management

The first pillar of Risk Based Process Safety Management is “Commitment to Process Safety.” A formalized mentoring system can ensure workforce involvement, compliance with company and regulatory requirements, increase the competency of personnel and enhance the process safety culture of the entire organization. Within this element there are several essential features that lead to a more effective process safety culture. Providing strong leadership is critical for any organization that strives to manage the risk associated with the activities associated with process safety. Leadership is a skill that is not necessarily intuitive to managers and mentors. Leadership is a skill that can be learned. In this Tip of the Month (TOTM), we explore process safety leadership.

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22 Apr, 2014

Simple Equations to Approximate Changes to the Properties of Crude Oil with Changing Temperature

This article describes simple equations to approximate changes to the properties of crude oil with changing temperature. Changes in crude oil density and specific heat, or heat capacity, can be estimated from graphs and/or more elaborate computer simulation. The latter generally requires access to a process simulator and characterization data for the crude oil. A suitable, tuned computer model is likely the most accurate method of estimating the fluid properties, but is not always available. Direct laboratory measurement is also possible if facilities and oil samples are available and a high degree of accuracy is required.

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11 Feb, 2014

Acid Gas-Water Content

This post goes over the acid gas-water phase behavior system. Specifically, different methods of predicting water content of acid gas systems are evaluated based on experimental data from the literature. Water content diagrams compatible with the experimental data for pure CO2, Pure H2S, pure CH4 and their mixtures are generated and presented. These charts can be used for facility type calculations and trouble shooting.

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14 Jan, 2014

Visit us at these conventions in 2014!

PetroSkills will be attending the following conferences in 2014. As always, these events give us a wonderful opportunity way to speak with industry professionals, hear feedback, discuss solutions, network, and identify the best ways to work together to improve competency for you and your organization.

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16 Dec, 2013

Estimating TEG Vaporization Losses in TEG Dehydration Unit

In this Tip of The Month (TOTM), the effect of striping gas rate and triethylene glycol (TEG) circulation ratio on the TEG vaporization loss from the regenerator top and contactor top is investigated. Specifically, this study focuses on the variation of TEG vaporization losses with reboiler pressure, TEG circulation ratio and stripping gas rate. By performing a rigorous computer simulation of TEG regeneration at reboiler pressures of 110.3 kPaa (16 psia) and 524.1 kPaa (76 psia), several charts for quick estimation of TEG vaporization losses from regenerator top and contactor, which are needed for facilities type calculations are developed. In addition, the effect of contactor temperature on the TEG vaporization losses for a case study is shown.

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19 Nov, 2013

Excellence in Workforce Development - Part 1

The SMRP Body of Knowledge is the best there is. But how do you know if your people can demonstrate their competence? How are you going to replace your retiring, experienced personnel with competent people who can perform on the job? How do you manage safety with safe work behaviors by competent people? In a growing number of societal areas, we are using ‘leading indicators’ to help people choose safer behaviors that prevent accidents.

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