A simple NMR methodology for evaluating filter cake properties and drilling fluid-induced formation damage

Abdulrauf R Adebayo,Badr S Bageri

doi:10.1007/s13202-019-00786-3

Abstract

An efficient drilling fluid will form a filter cake that will minimize the drilling fluid invasion into any drilled formation. Drilling fluid must therefore be adequately evaluated in the laboratory prior to field trial. Filter cake properties such as thickness, porosity, permeability, and pore structure are frequently evaluated using several techniques such as CT scan, SEM, and XRF. However, each of these techniques can evaluate only one or two filter cake properties. This paper presents a simple but novel NMR technique to evaluate filter cake properties such as thickness, pore volume, porosity, and possibly permeability. Furthermore, the amount and particle size distribution of solids that invaded a given rock sample can be obtained using the same technique. The full procedure was tested and verified using four identical rock samples. Drilling fluid invasion and filter cake deposition experiments were conducted on each of the samples, using the same drilling fluid but four different concentrations of fluid loss additive. NMR T2 relaxation measurements were taken at three different stages of each rock sample: before filter cake deposition; after fluid invasion and filter cake deposition; and after filter cake removal. A material balance analysis of the probability density function and cumulative distribution function of the measured T2 profile at the different stages of each sample yielded multiple filtration loss properties of the filter cake. The results obtained showed high accuracy of the NMR versus the current techniques. Moreover, this current method evaluated the majority of the filter cake properties at the same time and in situ hence eliminated the need of using multi-procedures that disturb the sample state. Finally, the presented method can also be used to evaluate secondary damage associated with filter cake removal process.

Highlights

Formation damage impairs well deliverability, injectivity, drainage efficiency, and hydrocarbon recovery
Minimal and shallow particle invasion is required for filter cake deposition over the face of the drilled formation, uncontrolled and unrestricted invasion of these particles can have an adverse effect in the near-wellbore region
The methodology covers the use of NMR measurements to evaluate filtration properties of drilling fluid and the formation damage arising from filtration

Summary

Introduction

Formation damage impairs well deliverability, injectivity, drainage efficiency, and hydrocarbon recovery. Formation damage can be caused by many operational factors such as clay swelling, fine migration and deposition, particle invasion, and plugging during drilling operations. Amaefule et al (1988) classified frequently encountered formation damage mechanisms into two broad categories. The first category is the damage caused by fluid–fluid interactions Drilling fluid invasion during well drilling is usually the first source of formation damage. Minimal and shallow particle invasion is required for filter cake deposition over the face of the drilled formation, uncontrolled and unrestricted invasion of these particles can have an adverse effect in the near-wellbore region. The formation permeability can be significantly reduced such that future or enhanced

Methods

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Conclusion