SEARCH FOR OIL

Wairarapa Times-Age, 19 August 1938, Page 10

SEARCH FOR OIL

4, ACTIVITIES IN TARANAKI. IMPROVED METHODS IN USE. An account of the progress made in the methods of prospecting for oil was given by Mr A. A. Weymouth, an American geologist at present engaged on the work in Taranaki, to the New Plymouth Rotary Club. “Geology has established the relationship, between oil and underground rock formation,” said Mr Weymouth. “When oil prospecting first started the average was usually about 30 dry wells to every oil producing well, but this now stands at about six to seven oil producing wells to every ten put down. Rock formations were roughly divided into three classes —sedimentary, igneous, and metamorpheus—but sedimentary rocks were really the only ones actively to interest the oil prospector. Under this category came sandstone, limestone, and shale. Sedimentary formations had all at one time or another been laid under the sea or water and as a consequence contained phosphorous as evidence of marine life.

ROCK FORMATION. Sedimentary rock formations in their turn were divided into two classes, anticline and syncline. The anticline or dome formation usually indicated the presence of oil, and it was on this theory as worked out by a noted oil geologist, Mr F. G. Clapp, that almost all the present prospectors worked. Mr Weymouth said that the sedimentary rock must be porous enough to hold the oil and there must also be some source from which the oil had been generated. There was some doubt how oil was generated. but the presence of marine growth was regarded as an essential. That fish oil was the basis appeared to be the generally accepted theory. Water. conditions arid the presence of. porous cover such as shale were also important. RECONNAISSANCE FIRST. In a geological, search one went ahead with a reconnaissance while a larger party followed his activities by careful mapping and surveying. In the present search in Taranaki, Mr Weymouth said, he was carrying out the reconnaissance while other parties at Whangamoana and Ohura were proceeding with the detailed work. Various instruments had been used from time to time in attempts to determine the rock formations under the subsoil, but they were bound to possess serious defects. In the past two or three years,, however, an advance was made by the introduction of the sycomograph, which worked on the principle of the pendulum. This irii4 eluded the use of the phonic depth finder. There were two methods' but the reflectory was the one in general use. A charge of dynamite was fired at a depth of about 50 feet arid the effects recorded on the sycomograph, from which accurate deductions could then be made as a result of knowledge of the vibrations caused. The results. obtained by this method were remarkably accurate, but as Mr Weymouth added with a smile, “The only real test is the result of the boring of the well.”