An apparatus (312) for use in a wellbore (304) is provided to compensate for pressure differentials between fluid in the wellbore and fluid in an oil bearing formation therearound. In one aspect of the invention, an apparatus is provided for insertion in a string of screened tubulars (306) in a horizontal wellbore. The device includes an inner tubular body portion (306) having apertures (308) in the wall thereof for passing oil, an outer tubular body (324) and a pathway therebetween (305) permitting oil from a formation to migrate into the inner body. Disposed around the inner body is an axially movable member (311) to selectively cover and expose the apertures of the inner body, thereby permitting fluid to flow therethough.