Andre Leibsohn Martins

Comportamento reológico de xantana produzida por Xanthomonas arboricola pv pruni para aplicação em fluido de perfuração de poços de petróleo

The aim of this work was to evaluate xanthans produced by Xanthomonas arboricola pv pruni to be used for increasing the viscosity of fluids applied in the perforation of oil wells, which were compared with three commercial samples. In order to do that, the viscosity of aqueous and saline solutions (NaCl, KCl and CaCl2) from different xanthans, at different temperatures (25, 45, 65 and 80 oC), was determined in a rheometer. The rheological parameters consistency index (K) and flow behaviour index (n) were obtained by adjusting the data with the Ostwald-de-Waelle model. Gel strength (G0, G10 e G30) was determined in a viscometer, and the concentration of monovalent (sodium and potassium) and divalent salts (calcium and magnesium) was determined in flame photometer and in atomic absorption spectrometer, respectively. Taken together, the results obtained in this study showed that xanthans produced by patovar pruni, Xp 106-600 and Xp 115-600, are promising for fluids used in oil well perforation with saline solutions, because they have low concentration of salts. As for the commercial polymers, they presented the best results when used in aqueous solution, because they had high salt concentrations.

A Mechanistic Model for Horizontal Gravel Pack Displacement

This article presents the detailed formulation for each of the three steps of a horizontal gravel pack displacement operation, including sand injection and alpha/beta waves propagation. The main core of the model, aiming the definition of alpha wave height, is based on a well known two layer model. Initially developed for hydrotransport applications, this kind of model has been adapted by several authors for drilled cuttings transport analysis. Besides, a comparison between theoretical predictions and pumping charts from a field operation performed in Campos Basin is presented. Gravel Pack, Modelling, Sand Control, Stratified Flows

Optimizing Cuttings Circulation in Horizontal Well Drilling

The action of stopping drilling to circulate the cuttings out of the well is always a point of controversy among oilfield teams. The practice of circulating periodically the hole may avoid several operational problems during the drilling of horizontal well. On the other hand, if hydraulic minimum requirements for the cuttings bed removal are not achieved, circulation can be ineffective, time consuming and, in some cases, detrimental to wellbore stability. This paper presents a series of large scale lab experiments which aimed at the investigation of the erosion of a cuttings bed deposited on the lower part of a horizontal annular section. A group of correlations, based on the experimental data, was developed to predict bed height and critical flow rate for bed removal as functions of several independent variables. The proposed methodology, coupled with a cuttings transport numerical simulator, is an useful tool for programming effective circulation of cuttings bed.

Planning Extended Reach Wells for Deep Water

In Brazil, major oil fields are in deep water, and extended-reach wells (ERWs) may be the only technically and economically viable solution for development. To drill ERWs in deep water from a floating vessel, such as a semisubmersible rig or a drill ship, is much more complex than performing the same job onshore. An R&D project was created to develop techniques and operational procedures for drilling those wells.

Foam Rheology Characterization as a Tool for Predicting Pressures While Drilling Offshore Wells in UBD Conditions

The use of foam is a highly attractive alternative for drilling depleted, loss circulation or gas zones. Due to its complexity, a foamed system requires special attention while designing field operations. This paper summarizes an extensive experimental program developed at PETROBRAS R&D Center facilities, coupled with a set of real scale tests under foam circulation conditions and numerical simulations, aiming the development of a comprehensive and useful model for predicting bore hole pressures while drilling under-balanced or near balance with foams. The lab work steps include foaming agent selection, rheology lab equipment development and/or adaptation, definition of test procedure and matrix, besides discussion and analysis of results. After about 60 rheology tests performed in several lab and pilot scale equipment, correlations were proposed to predict rheological parameters as functions of foam quality. Based on the experimental data, a set of correlations was developed to predict foam rheological properties as functions of base fluid rheological properties and foam quality. The next step was to evaluate the lab results by comparing pressure predictions with experimental data obtained by circulating different quality foams in a real scale vertical well located at PETROBRAS Training Center. The proper fitting of the proposed model and the experimental results supported its implementation in PETROBRAS lightweight fluid drilling software.

Physical Properties of Cuttings, Drilling Fluid and Organic Phase Recovered in the Drying Operation in Oil and Gas Well Drilling

Oil companies have increasingly invested in alternative technologies for cuttings treatment. The research for new operations or equipments leads to investigate the properties and characteristics of drilled cuttings and drilling fluids. This work presents the physical characterization of cuttings, drilling fluid and organic phase recoved after cuttings drying. It was carried out analysis of rheology for the drilling fluid and particle size and shape for the cuttings. Considering the microwave drying technology, which has been investigated for cuttings treatment, it was also determined the dielectric properties for the drilling fluid. The quality of the organic phase recovered in the microwave cuttings drying was also analysed.

Analysis of Interface Between Newtonian and Non-Newtonian Fluids Inside Annular Eccentric Tubes

In this work, flow of two adjacent fluids through annular eccentric tubes is analyzed numerically. This kind of flow is found in cementing processes of oil wells, where the cement paste pushes the drilling mud through annular space between the drilling column and the oil well wall. Both drilling mud and cement paste behave as non-Newtonian fluids, and between then a wash fluid is usually used, to avoid their contamination. The analysis of interface configuration between these fluids helps to determine contamination, and is an important tool for the process optimization. The numerical solution of the governing conservation equations is obtained via the finite volume technique and the volume of fluid method, using the Fluent software (Fluent Inc.). The effects of rheological parameters and eccentricity are investigated, for different flow rates. The results obtained show that the displacement is better when a more viscous fluid is used to push the other fluid. Also, it is observed that the interface shape is a function of flow regime and viscosities ratio. However, it is insensitive to eccentricity.Copyright

Drill-In Fluids: Identifying Invasion Mechanisms

Fluid invasion into productive zones is recognized as detrimental to well productivity. Filtrate and solids invasion can cause irreversible formation damage and permeability reduction. Nondamaging acid-soluble solids are added to drill-in fluids to promote pore plugging and minimize fluid penetration. Development of less invasive, nondamaging fluid formulations requires knowledge of filtration mechanisms of solids-containing polymeric solutions in porous media.

Dynamic Aspects Governing Cement-Plug Placement in Deepwater Wells

Plug cementing is still considered to be a critical operation and cases of failure eventually happen. Large annular gap and eccentricity, typical of these operations, are factors which may promote unstable flows resulting in cement slurry contamination. Deepwater conditions enhance chances of free fall, and consequently, low displacement velocities can occur in the annulus[1]. This article presents a parametric study in the role of rheological properties of fluids (drilling fluid, spacers and cements slurries), string rotation, flow rates (including free-fall effects, where due the differences between density of the fluids the injection flow rate is different of return flow rate) in the displacement quality of cement plugs. Analyses are based on 2 different simulation tools. Conventional cement pumping softwares define flow rate profiles at annulus entrance, accounting for free fall effects and CFD simulation to define interface propagation and contamination levels. The main issues addressed by the simulations are how to optimize density and rheology hierarchy which minimizes contamination and avoids channeling The compilation of simulation results in useful guidelines and procedures for displacing cement plugs in vertical inclined and horizontal offshore wells.

A Comprehensive Methodology to Analyze The Impact of the Sand Control Technique on the Efficiency of an Horizontal Well

Abstract. Sand production in unconsolidated formations has brought heavy injury for the oil and gas industry around the world. Million dollars have been invested in sand control techniques. Among the several sand control systems existing, Open Hole Gravel Pack (OHGP) is the one adopted for horizontal well completions in the offshore Brazilian fields. With the experience in the development of such fields, some assets start to consider the adoption of less conservative sand control strategies, such as the use of stand alone premium screens (SAS). The present work proposes a methodology for evaluating the impact of the sand control technique in the productivity or injectivity of a horizontal well. Several parameters, such as damage rate (DR) and productivity or injectivity index per horizontal effective length (PI/Lef) were used to compare similar wells equipped with different sand control techniques. The main goal of the study is to address the following questions: Is there any formation damage due to the gravel pack during production lifetime of a well? The wells equipped with stand alone screen exhibit formation damage? Wells equipped with OHGP have the same performance when compared with wells equipped with SAS? Stand alone completion is a good alternative path for multilateral and extend reach wells?