Augusto Garcia-Hernandez

Determination of Cuttings Lag in Horizontal and Deviated Wells

A literature review, preliminary modeling, preliminary experimental work and recent development of this project are presented in this report. The literature review has been focused on cuttings transport in horizontal and slightly inclined well-bores, solidliquid flow patterns (two and three layer models), particle slip velocity and particle tracking. To model the phenomena, correlations developed by Larsen, Iyoho 12 and Chien were used to calculate the particle traveling velocity, and then it was used to associate the particles with their original location using other relationships. Preliminary experimental work has been completed using the Low Pressure Ambient Temperature Flow Loop (L.P.A.T.) and a high speed camera. Due to a recent development the current report includes a suggested modification of the flow loop in order to record the bed height in the inclined condition.

Energy Usage in Natural Gas Pipeline Applications

Energy required to transport the fluid is an important parameter to be analyzed and minimized in pipeline applications. However, the pipeline system requirements and equipment could impose different constraints for operating pipelines in the best manner possible. One of the critical parameters that it is looked at closely, is the machines’ efficiency to avoid unfavorable operating conditions and to save energy costs. However, a compression-transport system includes more than one machine and more than one station working together at different conditions. Therefore, a detailed analysis of the entire compression system should be conducted to obtain a real power usage optimization. This paper presents a case study that is focused on analyzing natural gas transport system flow maximization while optimizing the usage of the available compression power. Various operating scenarios and machine spare philosophies are considered to identify the most suitable conditions for an optimum operation of the entire system. Modeling of pipeline networks has increased in the past decade due to the use of powerful computational tools that provide good quality representation of the real pipeline conditions. Therefore, a computational pipeline model was developed and used to simulate the gas transmission system. All the compressors’ performance maps and their driver data such as heat rate curves for the fuel consumption, site data, and running speed correction curves for the power were loaded in the model for each machine. The pipeline system covers 218 miles of hilly terrain with two looped pipelines of 38″ and 36″ in diameter. The entire system includes three compressor stations along its path with different configurations and equipment. For the optimization, various factors such as good efficiency over a wide range of operating conditions, maximum flexibility of configuration, fuel consumption and high power available were analyzed. The flow rate was maximized by using instantaneous maximum compression capacity at each station while maintaining fixed boundary conditions. This paper presents typical parameters that affect the energy usage in natural gas pipeline applications and discusses a case study that covers an entire pipeline. A modeling approach and basic considerations are presented as well as the results obtained for the optimization.

Centrifugal Compressors During Fast Transients

Transient studies for compressor systems allow the prediction of the compressor system behavior during fast transients such as they occur during emergency shutdowns. For the system simulations, the compressor behavior is assumed to be quasi-steady-state. This means in particular that the steady-state compressor flow-head-efficiency-speed map remains valid. During well instrumented emergency shutdown tests conducted on a centrifugal compressor system under realistic operating conditions, data showing the head-flow-speed relationship of the rapidly decelerating compressor were taken. These data are compared with steady-state head-flow relationships taken at a number of speeds. This allows the determination of the relative deviation between the transient and steady-state head-flow-relationships and thus answers the question of the validity of steady-state assumptions during rapid transients. The impact of the fast transients on efficiency and consumed power, which can be derived from the speed decay of the system, as well as the impact of nonstationary heat transfer are also evaluated and reported.

Transient Surge Measurements Of A Centrifugal Compressor Station During Emergency Shutdowns.

For every centrifugal compressor installation, the design of the surge control system is vitally important to prevent damage of the compressor internal components, seals, and bearings. While most surge control systems are capable of preventing surge for steady-state operation, emergency shutdowns (ESDs) are particularly challenging, since the surge control system must respond faster than the deceleration rate of the train. The available experimental data are not of sufficient quality and resolution to properly validate current software packages. This paper outlines an experimental test program using a full-scale compressor tested in a hydrocarbon flow loop under controlled, laboratory conditions. Transient compressor surge data during an ESD were captured over a variety of initial speed, pressure, and flow conditions. Furthermore, the anti-surge valve was modified in subsequent tests to simulate a slower and a smaller valve, providing a more varied test condition. Results of the testing and model comparisons will be presented.

Simulator To Train Operators On Newly Installed Pumping Equipment

New screw pumps were installed at an existing offshore oil platform that originally housed only centrifugal pumps, thus creating the need to safely train operators on the new equipment. Therefore, a training simulator was developed with control screens identical to those provided by the manufacturer providing a safe and low-cost way for training operators. The simulator was designed with the ability to control the entire pumping system, so that any operating scenario could be created in addition to the preloaded cases. Screens were added to provide insight into the operating behavior of the system and to allow the chance to try alternative operating procedures. The simulator developed provides a means for the platform operators to comply with API 1120, ASME B31Q, RP 1161 and RP T-2. This paper will focus on describing the need for creating a training simulator, the approach to creating the simulator, will present some example screenshots, and present the system insight that is gained by allowing operators to learn about the system hydraulics.

A New Risk and Reliability Model for Compressor and Pump Installations

Compression and pumping systems are constantly changing infrastructures, with many of the older compressor/pumping stations requiring updates, repairs and inspections to maintain safe and efficient operations. These stations operate over a wide range of pressures, flows, and working fluids under varying environmental conditions. Operating condition factors, as well as original design and materials, can significantly affect corrosion rates, structural integrity, and the flow capability of these compressor/pumping stations. Station equipment can be logically inter-related using failure trees and each critical sub-component be assigned a mean time between failure and failure probability using acceptable industry standards. These individual components are then allowed to interact to determine sub-system, system, and full station level failure probabilities. This type of analysis has historically not been utilized by the oil and gas industry but is common to other industries, such as the aerospace and nuclear power industries.This paper presents a new, comprehensive, consistent, and effective process for predicting risk, integrity, and reliability of the compressor and pump stations as well as each major subsystem and component within these stations. The model considers predefined “threats” such as mechanical, materials, electrical, third party, environment and external forces, improper maintenance, and operation of all its components; thus, typical failures modes are included in these threats. A semi-quantitative methodology with factored risk indices is applied where weighting factors are used to adjust the model with operational data. These factors are generated from reliability data extracted from the station. Comparisons between the model predictions and the reliability data will allow tuning of the weighting factors. Weighting factors are defined for each of the identified threats. The probability of failure is computed at a component level; however, it can be obtained at any level in the system based upon the specified categorization. The probability of failure is represented as a function of three factors: exposure, resistance, and mitigation, while the consequence of failure is estimated using the same approach based on three factors: receptor, hazard, and reduction.This predictive risk and failure model has been defined based on international specifications and is consistent with actual operating conditions, capacity planning, and remaining life expectations, while assuring that the stations meet the day-to-day operational demands of the system. The model also is able to predict each individual equipment failure probability within the station systems and provides for easy output of the data in graphical form for proper operating, maintenance, repair, and testing decisions.Copyright

Dynamic Pipeline System Simulation of Multi-stage Compressor Trains

An oil and gas company was facing process and mechanical related problems on the multiple-stage compressor trains at two important booster installations. The frequency of these problems has increased lately, and this has led to frequent trips and shut downs. These interruptions affect the operation of the plant leading to a loss in production and consequences of lost revenue for the company. The two platforms each contain one compressor train comprising a four-stage compressor with a gas turbine driver. Each train is fitted with an integrated turbine compressor control panel.Thus, a detailed dynamic pipeline system simulation of the subject compressor trains was performed in order to provide a series of recommendations that would improve the safe operation and increase the reliability of the compression systems. The analysis included a review of the existing compression systems including all the equipment and hardware related with the compression anti-surge system. In addition, a site visit was performed to review and understand the existing anti-sure control system at each facility. A detailed dynamic model of the multi-stage compression system was built for each train. These models included compressor performance maps, gas compositions for each stage and train, piping yard, recycle, isolation, check and blowdown valves, scrubbers, separators, and coolers.Several simulation cases were conducted for both the platform systems. These cases evaluated the effect of the delay and travel times of the existing anti-surge valves, delay the coast down action, failure of the non-return valves (NRVs), action of a blowdown valve on the emergency shutdown (ESD) sequences, recycle valve bypasses, check valve arrays, and process upset conditions. In addition, parametric studies were conducted for each of the most important parameters of the system to quantify their effect of any possible modification.The results of this analysis provide recommendations to solve some of the existing issues while understanding more of the dynamics of the system. It was found that any propose recommendation or change in the sequence or timing of one stage will affect the surrounding stages since they are not only connected through the piping as they are driven by the same gas turbine shaft. Therefore, a very comprehensive analysis was conducted for each train to provide recommendations that would be feasible for implementation while reducing the constant risk of mechanical failure and surge events. Thus, results of the analysis and some of the recommendations obtained are presented in this paper.© 2012 ASME

Acoustic Leak Detection Technology Assessment

Leak detection systems are a vital part of a pipeline integrity management program. For liquid hydrocarbon pipelines, these leak detection systems can take the form of measuring conditions inside the pipeline (internal detection) or by use of hardware installed outside of the pipe (external detection). One internally-based technology is acoustic leak detection, sometimes known as rarefaction-wave monitoring. This technology is based on detecting transient pressure waves that are generated when a sudden leak occurs. Acoustic pressure waves travel in the pipeline at the speed of sound of the fluid that is being transported and can be detected by dynamic pressure sensors. Various filters and algorithms can be used to identify this disturbance and distinguish it from other pressure events on the pipeline. This architecture can even be used for noise and for signal pattern recognition to allow for automatic alarming of potential leak events. Each manufacturer of such technology applies unique algorithms or processing methods to capture and analyze the pressure signals that are used to later predict leaks and their locations.This paper presents a comprehensive review of the technical basis and methodology employed by acoustic leak detection systems in order to further understand their capabilities and limitations. This work included a vast amount of hydraulic modeling aimed at understanding the physics of wave propagation caused by leak events. Diverse parameters, such as initial pressure wave amplitude, signal attenuation, flow and pressure dependence, speed of sound effects, and sensor locations were evaluated. This modeling was conducted for a variety of simulated fluids. A proportional relationship between leak rate and the initial pressure disturbance caused by a leak was obtained. This linear trend can be used in combination with an attenuation model to calculate sensor location limitations. The work determined that the uncertainty in the speed of sound for a pipeline fluid segment significantly impacts the error bands of leak location. The modeling was used to generate correlations for signal attenuation over distance as a function of pipeline conditions.Copyright

Hydraulic Modeling And Simulation Of Pumping Systems

Research Engineer at Southwest Research Institute, in San Antonio, Texas. His professional experiences include various experimental works, sales, technical support, drilling research assistant, and drilling laboratory teaching assistant. His Master’s thesis focused on cuttings transport velocity in horizontal and highly-inclined wells. In addition to his graduate work, he has been involved in research on double-piston pumps (experimental characterization and evaluation) and progressive cavity pumps (modeling development), as well as drilling fluids applications. Mr. Garcia has publications in areas such as cuttings transport in horizontal and deviated wells, gas and liquid pipeline transport, and centrifugal compressor surge analysis. Mr. Garcia-Hernandez holds a B.S. degree (Mechanical Engineering) from Central University of Venezuela and an M.S. degree (Petroleum Engineering) from the University of Tulsa.