"BRINGING IN" WELLS a strictly "wild-cat" country, only the geological informa tion gathered in the field may be employed as to the proper horizon that is looked for. In most instances, however, although wells are some distance from production, the various strata are well known and the formations recognized from past experience.
From the elevation of the well, which has been determined at the time the well location was made and surveyed, the depth at which the sand is expected may be figured very closely. As the drill approaches the sand, the samples from the bailer are carefully washed and laid out in order, the operator and drillers are enabled to tell from such samples when the top of the sand is reached. A steel line measurement always be taken at this point, and the drilling proceeds. It is customary, espe cially in an unknown country, to be prepared for the possibility of striking a large volume of gas, by laying a snuff-line from the boiler to the mouth of the well; in case gas is struck unexpectedly, the steam under pressure from the snuff-line is turned on so that it mixes with the gas and disperses it, so that the risk of fires may be minimized. All fires around the rig are to be extinguished at once, the boiler allowed to cool and moved to a safe distance. The direction of the wind is always to be watched, as it may blow in the direction of the boiler, and gas with it will be a source of danger.
When the top of the sand is reached and its depth determined, the drilling is resumed. The presence of gas may be noted at the well mouth and is to be gauged after each "screw" with the Pitot tube. The presence of oil is determined by noting the contents of the bailer, in which it will be brought up if there is any present. Water is to be watched for and if the sand's color changes and turns white, water is indicated. If there is oil in the hole the water is not to be drilled into more than a font, so that the incoming water will not be too much and yet move the oil with it, thereby bringing a larger amount of oil into the hole. The size of an oil well can be estimated only at the time
it is drilled in. This may be done by noting the rapidity with which oil fills up in the hole, as noted on the drilling rope, when the tools are withdrawn; the space taken up by the tools as well as the •possibility of water being under the oil must be con sidered. The amount of oil flowed, swabbed or bailed out during the first twenty-four hours is the general report that is given out in most cases.
The surest method of valuing an oil well is after it has been pumped or allowed to flow for some time. In the case of large gushers, the amount of oil produced is known only if properly tanked. The production of oil out of a new well is known as its flush production, and in the course of some time, varying from six months to a year, a well will settle down, and when it is known to have a settled production. Wells are generally bought and sold with the settled production in mind.
Very little can be told from the examination of the sand brought up in the bailer; however, whether it is soft or hard and the shape of the grains as well as their size may be determined. When water, especially hot water, is poured on the sand, the rainbow colors of petroleum may be seen if any amount is present. Oil. men consider all sands that produce oil as good sands, and others as "no good." Although in the true sense of the word all this is true, still the appearance of the sand may explain the bad results of a well, and although this may be a post-mortem information, it may be put to good use in future drilling, by noting the variation of the texture of the sand from place to place, and as such variations may take place gradually, such knowledge is worthy of consideration.
A sand body may have one or more pay streaks, which are generally divided by a closely cemented portion of sand, or by thin shale stratum; such conditions are indicated by the drillers as breaks. Breaks may divide a sand into several pays, or again it may be the dividing point between oil and water.