A New Method Of Determining Range And Direction From A Relief Well To A Blowout Well

Abstract

A method utilizing four component-type magnetic sensors for the determination of range and direction from a relief well to a blowout well is presented. The advantages of using component-type magnetometers and magnetic gradient information are enumerated. The equipment and its operation are described. Typical examples of results obtained in field operations are given and their analysis is discussed. Introduction There are few events more frightening than a fiery catastrophic blowout on an offshore drilling platform. In an astonishingly short time the rig disintegrates and sinks onto the ocean floor, leaving only a huge gas bubble boiling through the water's surface. If the escaping gas does not continue to burn, it is generally ignited for safety. Onshore blowouts can be equally devastating, particularly if the surface conductor is not particularly if the surface conductor is not accessible. Under either of these circumstances the most successful way to bring the blowout well under control is to drill a relief well directed so as to intersect the blowout well, or to get sufficiently close to the blowout well at the problem area so that fluid communication between the two wells can be effected. Thereafter the kill attempt can be accomplished and the blowing well brought under control. See Figure 1. As simple as this procedure may appear, the exact location of the relief well and the blowout well at depth are seldom known with sufficient accuracy to assure an effective kill operation. The principal reason for this is that well surveys are typically made with precisions no greater than a quarter of a degree. At a depth of 10,000 feet this means that each well may be anywhere within a circle of 87 feet diameter. Furthermore, additional cumulative deviations can occur in both wells which would substantially increase the areas of these circles of uncertainty. In the worst case, the two wells may be too far apart to establish communication by any reasonable means. In the critical situation of attempting to control a blowout well, the range and direction from the relief well to the blowout well must be known. In late 1975, Houston Oil and Minerals Corporation commissioned Tensor to develop a system for making such measurements. P. 1

Directional Survey and Proximity Log Analysis of a Downhole Well Intersection

“…A second method of determining the proximity to casing uses a magnetic technique developed and marketed by Tensor Inc. 2 This technique gives infonnation about both direction and distance to the casing in a blowout well. The magnetic-field gradient associated with the casing couplings or some other metal in the blowout well is used to detennine the distance and direction to the target.…”

New Uses of Existing Technology for Controlling Blowouts: Chronology of a Blowout Offshore Louisiana

“…The MAGRANGE borehole survey is a down-hole magnetometer influenced by the pipe in the uncontrolled well. 5 In addition, two other tools, the Ultra Long Spaced Electric Log (ULSEL) and the Borehole Audio Tracer Survey6 (BATS), were capable of determining the distance between the relief well and the blowout well. The ULSEL instrument records the abnormal resistivity of the formation caused by the casing in an uncontrolled well.…”

“…A pollution control unit was on location to contain any possible pollutants. 5. Two barges equipped with water-spraying facilities were placed under contract, and by mid-afternoon, one barge arrived on location and began spraying water to prevent ignition.…”