Patent ID: 8813846

Claim:
A method of treating a fractured hydrocarbon bearing formation penetrated by a well, the fractured hydrocarbon bearing formation having a formation temperature, a rock matrix formed of carbonate and matrix oil wetting the rock matrix, the rock matrix having fractures, the method comprising: in a first phase, injecting a formation compatible aqueous fluid into the fractured hydrocarbon bearing formation through the well upon which the formation compatible aqueous fluid penetrates the fractures, heats the rock matrix and the fractures fill with the formation compatible aqueous fluid and matrix oil expelled from the rock matrix; in the first phase, allowing the well to soak and cool off in a soaking period during which the rock matrix is filled with matrix oil and partially filled with formation compatible aqueous fluid from oil contraction during soak and cool off; in the first phase, opening the well to allow production of matrix oil and formation compatible aqueous fluid; in a second phase, injecting a hydrocarbon solvent into the fractured hydrocarbon bearing formation through the well to dilute the matrix oil by solvent diffusion into the matrix oil, the hydrocarbon solvent having a boiling point and being miscible with the matrix oil, during which second phase, the fractures fill with hydrocarbon solvent; in the second phase, closing the well to allow the fractured hydrocarbon bearing formation to soak in the hydrocarbon solvent, while the rock matrix fills with matrix oil, matrix oil and diffused solvent mixture and formation compatible aqueous fluid; in the second phase, opening the well to produce a mixture of matrix oil and hydrocarbon solvent, while the fractures drain matrix oil, at least in a third phase, repeating the first phase after the second phase, including the closing of the well, soaking of the fractured hydrocarbon bearing formation and production of matrix oil, in which third phase the formation compatible aqueous fluid has a temperature selected to be sufficiently close to the boiling point of the hydrocarbon solvent that boiling of the hydrocarbon solvent in the fractured hydrocarbon bearing formation in the third phase drives hydrocarbon solvent out of the rock matrix for retrieval of hydrocarbon solvent; and producing hydrocarbons from the fractured hydrocarbon bearing formation.