INCREASING PRODUCTION an attempt to get the full benefit of the oil or gas in the pay sand,' it requires careful attention and the employment of such handling as will bring the desired results.
The ordinary methods require that the wells be taken care of in a proper manner, and under such handling the production from oil wells is obtained so long as the gas pressure is sufficient to move the oil from the rocks into the well. When the ordinary methods fail in further production, various means are at hand with which an increase in the production may be brought about.
From the facts mentioned in connection with the theoretical and the effective porosity, it will be noted that only a small percentage of the total amount of oil in a given sand is removed, while the greatest portion of it will remain in the sand owing to the fact that the general method of recovery, which is by means of pumping, is not sufficient to recover the total amount of oil from the sand. As long as gas pressure is greater than the ordinary atmospheric pressure. such pressure will move the oil towards the opening, but when it has declined so that it is unable to bring the oil with it, several systems are put in use in order to assist or reproduce the pressure previously existing in the sand. For this purpose the various processes that have been employed are: the use of vacuum, flooding, introduction of compressed air or compressed gas; in each case it will be noted that the resulting pressure is the main factor that is employed.
One of the oldest methods is the application of vacuum, by means of which the pressure at the wells is decreased, which allows the gas that may be in the oil to expand and work against smaller atmospheric pressure, thereby permitting the flow of oil into the well. Although production may be increased by this method its effect, however, is but temporary and the only reason for its employment is the fact that the increased gas production may be utilized for gasoline, as such gases are higher in gasoline content than the original casing-head gas, the other item being the increased production of the oil.
Flooding has been employed in several instances, the most notable being the case of Bradford, Pa., where the system has
been used with success, and the increased production of oil is obtained by allowing water to enter the sand, generally through a well down the dip, and as the sand is being filled with the water the oil is gathered in front of it and carried further up the dip into the wells that are located there. (Fig. 123.) The system is not recommended very highly, not only as it has been used successfully in but one case, but also because the flooding will practically end the usefulness of such a sand, and as other methods of greater promise may be tried that offer a chance for greater increase in production but which cannot be used after the sand has been so flooded. .
Another method in which water also plays a part has been patented by R. H. Johnson (Patent No. 1,o83,o18), which consists in drilling the hole through the oil sand into the water sand (where both occur in the same reservoir and the pressure has been reduced). Then by pumping rapidly a cone-shaped gradient is set up in the water table around the well, which will aid the movement of oil inward. (Johnson and Huntley, " Princi ples of Oil and Gas Production.") The most successful method so far employed is the intro duction of air or gas under pressure into the sand through small or abandoned wells properly fitted up to take the compressed gas, or air (air holes) (Fig. 124) and an attempt in reproducing the rock pressure in the sand is made. The air or gas, being under pressure, will force the oil through the sand and into the wells. The use of air or gas depends upon the circumstances that may exist, and both have their advantages and disadvantages.
In the case of gas, it is best employed where a large amount of it is on hand, otherwise the process would be expensive; its point in favor, however, is the fact that a gas so introduced may be regained and be richer in gasoline contents, which may be removed and the gas utilized again and this process repeated; that is, a gas from some well may be compressed and introduced into the wells and recovered richer in gasoline, the gasoline extracted, the gas again compressed and used in the wells again, sent through the same process.