Hydrocarbon resource companies in the Lloydminster heavy Oil region have experienced problems with unwanted gas flows to surface outside production and surface casings. Locating the source of these flows prior to attempting to shut the gas off has proved troublesome. Gas shut-off attempts have therefore had varying degrees of success ranging from failure to expensive success. This paper illustrates how conventional wireline gas detection methods, although successful in detecting gas sources in the Mannville sands, failed in the Upper Cretaceous horizons. Relatively unconventional wireline techniques are shown to be reasonably successful in locating these Upper Cretaceous gas zones. Studies prior to and after utilizing these unconventional techniques are also discussed. Finally, suggestions are made for wireline logging practices and remedial techniques. Introduction Unwanted gas flows to surface outside production and surface casings has become a matter of concern in recent years in the Lloydminster area. Aside from the obvious safety hazard posed by this problem, there can be severely detrimental environ-mental effects should the gas be allowed to migrate into the surrounding soil. Many cases of dead vegetation have been documented as a result of this gas migration.Quite often the unwanted gas flows to surface are not imme-diately obvious. Much of the time dead vegetation around a newly completed or abandoned well is the first indication that a problem exists in a newly explored heavy oil area. With this in mind, most hydrocarbon resource companies have begun to monitor the area around their wells with gas detection devices, especially in fields that are known to be gas prone.Conventional methods of downhole detection were attempted on individual wells. It was eventually discovered that these methods were inadequate. A modified system of gas detection resulted. The unwanted surface gas flow problem occurs in many areas around Lloydminster. The authors chose an area south and east of Lloydminster as a basis for this paper (Fig. 1). The results of the modified gas detection system in this area will be discussed in light of the historical and geological information available.