A method for enhancing production from multiple-fractured underground “tight” formations. Spaced upwardly-extending injection fissures are created along a horizontal injection wellbore, and upwardly-extending collection fissures, alternately spaced with the injection fissures, are created along the horizontal injection wellbore or another adjacent production wellbore. The injection wellbore is supplied with fluid under pressure, which flows into such created fissures and drives reservoir fluids within the formation to the remaining (alternately) spaced adjacent fissures along such wellbore or another parallel adjacent (production) wellbore, thereby allowing reservoir fluids to flow downwardly along such alternately spaced production fissures for collection. In a refinement, production is carried out initially from both the production and injection wellbores, and upon the rate of production of hydrocarbons slowing, production from the injection wellbore is stopped and a fluid is injected therein and thus into the formation via the alternate spaced fissures, thereby re-pressurizing the formation.