| 摘要 |
<p>The invention is concerned with a method and apparatus for determining the porosity of a formation surrounding a borehole. A drilling fluid penetrates a distance into the formation as a function of time. First and second measurement are taken, both at a first and at a second time. The first measurement is of a type selected to indicate a different porosity measurement in the presence of a gas as compared to the second measurement. The first and the second measurements are selected to have substantially the same depth of investigation into the formation and are affected proportionally by the gas.</p> |
