Process for finding the depth of a lost return zone

US5018589A · kind A · utility

Inventor

• James M. Williams · Palo Alto, US

Key dates

• Filing date: Jul 31, 1989
• Grant date: May 28, 1991
• Expiry date: Jul 31, 2009

Classification

• Technology area (CPC E): Fixed Constructions
• CPC primary: E21B21/003
• WIPO field: Civil engineering
• WIPO sector: Other fields

Abstract

In a process of downhole drilling in an open hole, where the drill bit has struck a lost circulation zone in the wall of the formation, and mud circulating through the annulus during drilling has been lost into the zone and therefore circulation of the mud has been lost, the process for locating the depth of the lost return zone would include the steps of (a) detecting a drop in the mud level within the annulus of the drill casing to a central depth; (b) introducing a quantity of lighter fluid such as 8.5 pound salt water into the annulus of the borehole so that the annulus becomes filled with the lighter fluid; (c) closing off any flow of fluid out of the annulus substantially at the level of the earth's surface; (d) pushing a quantity of the mud in the annulus into the formation by the weight of the lighter fluid flowing into the annulus; from the distance that the mud fell in the annulus, calculating the height that the mud did not drop in the annulus in order to have the same hydrostatic head of the lost return zone depth; following the establishing of the hydrostatic head, reading the gauge pressure of 5.45 pounds for every barrel pumped into the lost return zone; and multiply…