In times of overproduction such as the operators have been strugglingagainst for the past several years it is the practice of the oil industry toshut in certain wells in order to reduce the flood of oil. The purpose of thispaper is to present certain variations in production of oil wells when theoffset wells are shut in. The scope of the study has been confined toCalifornia fields, and more especially to those of the San Joaquin Valley.
The accepted definition of a shut-in well is a well where production hasbeen suspended by closing in the casinghead and tubing or by cessation of pumping. The immediate effect of such a procedure, of course, is to reduce theoil production from the lease, which is the result desired. However, it appearsthat certain types of wells vary widely in production of oil, gas and gasolineafter adjacent wells have been shut in, which variation has a very materialeffect on the ultimate recovery of oil from the property. The increase ordecrease in the oil production itself may not be of sufficient volume to occasion comment, but wide fluctuations in the gas and gasoline recovery underthe changed conditions are of the utmost importance in the future recovery of oil.
The scope of this paper includes:
the effect on producing oil wells ofshutting in offset wells, the wells being studied in three groups arrangedaccording to their relative stages of depletion;
probable source of excessgas and the effect on the ultimate recovery of oil;
suggested procedurewhen wells are shut in;
methods that could be employed to prevent unduemigration of gas from the shut-in area; and
the need for future studies ofthe situation.
For the purposes of this paper producing wells in California have beenarranged in three groups according to the age of the well, or to the relativestage of depletion of the producing zones. The first group consists of thosewells with a high fluid level, or in other words those wells whose fluid levelsare a considerable distance above the top of the perforations.