Scanning Electron Microscope Pictures of Reservoir Rocks Reveal Ways to Increase Oil Production
Authors: Holub R.W. , Noel R.P. , Weinbrandt R.M. 
Published: December 2007

This paper was prepared for the Society of Petroleum Engineers of AIME Symposium on Formation Damage Control, to be held in New Orleans, La., Feb. 7–8, 1974. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon requested to the Editor of the appropriate journal, provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract
This study attempts to explain the mechanisms of plugging that operate in oil wells. Using a Scanning Electron Microscope, together with flow studies on cores, our study points out that an oil-bearing formation is a most effective depth filter. it further shows that today's field practices, if properly modified, can greatly reduce formation damage and increase oil, production. Although formation damage cannot be completely eliminated, we deduce from our study many basic and simple ways to reduce it greatly. one such preventive approach, described below, was successfully applied in a small Texas field in sand control workover with less than one day payout.

Introduction
Our work attempts to answer the basic question Are oil wells being plugged by today's field operations and, if so, can this plugging be prevented? prevented? We have found that today's field operation do cause unnecessary plugging. Plugging cannot be completely prevented, but it can be greatly reduced. Any reduction in damage offers greater productivity, longer well life, and an increase in producible reserves.
WHY DO WELLS PLUG?
A close inspection of actual cores, in particular of individual pores within the cores by particular of individual pores within the cores by means of the scanning Electron Microscope (SEM), provides better understanding of the principles provides better understanding of the principles of plugging and points out some simple ways of preventing it. preventing it.

FORMATION PORES CONTAIN LOOSE PARTICLES
SEM of two typical oil-bearing sands from California (FIGURES 1 and 2) show many loose-appearing solid particles present within a single pore. FIGURE 1 depicts a pore entry (dark area in the center of the picture) at 460X magnification. All the sand grains shown are covered beyond shape recognition by small particulate matter. These particles are part particulate matter. These particles are part of the sand cementing matter of the West Coast Miocene oil producing sand. Since they may have been disturbed during the sample preparation, we focused on the wall inside of preparation, we focused on the wall inside of the pore in FIGURE 2. With 1870X magnification, we can see most of the particles, primarily clays, scattered at random.