Patent ID: 8826976

Claim:
A process for producing mineral oil from underground mineral oil deposits using microorganisms, in which at least one injection borehole and at least one production borehole have been sunk into the deposit, the deposit temperatures (T L ) are in the range from 45° C. to 120° C. and mineral oil is produced from the deposit, by injecting aqueous flooding media into the at least one injection borehole and producing mineral oil through the at least one production borehole, wherein the process comprises at least m process cycles Z 1 to Z m , in which each of the process cycles Z 1 to Z m comprises the process steps of (I) mobilizing mineral oil in the formation by injecting at least one aqueous formulation of oil-mobilizing microorganisms, nutrients and optionally an oxygen source, said microorganisms having an optimal growth temperature T w , and (II) injecting flooding water with a temperature of <45° C., the number of cycles is m≧2, process steps (I) and (II) are each performed in repeated alternating succession per cycle Z 1 to Z m , and T w of the injected microorganisms is not altered during the performance of each of cycles Z 1 to Z m , and in which the microorganisms used in each of process cycles Z 1 to Z m have a different optimal growth temperature T w , in the execution of the first process cycle Z 1 , microorganisms with the highest T w are injected, and in each new execution of process cycle Z, microorganisms which have a lower optimal growth temperature T W , than the microorganisms injected in the preceding process cycle Z are injected.