Analysis of Formation Damage Caused by Oil–Based Mud on Berea Sandstone Using SEM

Abstract

Objektif ujikaji ini adalah untuk mengkaji kerosakan yang dialami oleh batu pasir Berea berikutan penggunaan lumpur dasar minyak, dengan menggunakan Mikroskop Elektron Imbasan (SEM – Scanning Electron Microscope). Ujikaji dilakukan di makmal menggunakan lumpur dasar minyak sintetik (Sarapar 147) yang beroperasi dalam keadaan dinamik dengan tekanan pembezaan yang berbeza. Keputusan ujikaji dibincang berdasarkan nisbah kerosakan dan analisis secara visual imej SEM sampel teras yang terdedah kepada lumpur. Nisbah kerosakan yang dialami oleh sampel teras rosak didapati berkurangan apabila tekanan pembezaan meningkat. Imej SEM juga didapati memberikan keputusan yang sama. Imej SEM dan nisbah kerosakan turut membuktikan bahawa sampel yang dipasang pada sudut 180° (mendatar) mengalami penyumbatan partikel yang lebih ketara berbanding sampel yang dipasang pada sudut 90° (tegak). Kata kunci: Lumpur dasar minyak, kerosakan formasi, nisbah kerosakan, batu pasir Berea, SEM The objective of this experiment is to investigate the damage caused by oil–based mud on Berea sanstone using Scanning Electron Microscope (SEM). Laboratory experiment had been carried out using synthetic oil–based mud (Sarapar 147) at various differential pressures exerted on the core under dynamic conditions. The discussion of this research results were based on the damage ratio and visual observation of exposed samples using SEM. The damage ratios of the damaged core samples were found to decrease when the differential pressures were increased. These results were confirmed with SEM images. The SEM images and damage ratios also revealed that when samples were positioned at an angle of 180° (horizontal), they experienced higher particles plugging compared to samples positioned at an angle of 90° (vertical). Key words: Oil-based mud, formation damage, damage ratio, Berea sandstone, SEM