A process (20) to produce olefinic products suitable for use as or conversion to oilfield hydrocarbons includes separating (42) an olefins-containing Fischer-Tropsch condensate (64) into a light fraction (68), an intermediate fraction (82) and a heavy fraction (94), oligomerising (44) at least a portion of the light fraction (68) to produce a first olefinic product (72) which includes branched internal olefins, and carrying out either one or both of the steps of (i) dehydrogenating (50) at least a portion of the intermediate fraction (82) to produce an intermediate product (84) which includes internal olefins and alpha-olefins, and synthesising (52) higher olefins from the intermediate product which includes internal olefins and alpha-olefins to produce a second olefinic product (86), and (ii) dimerising (52) at least a portion of the intermediate fraction to produce a second olefinic product (86). At least a portion of the heavy fraction (94) is dehydrogenated (58) to produce a third olefinic product (96) which includes internal olefins. Also provided is a process (30) to produce paraffinic products suitable for use as or conversion to oilfield hydrocarbons which includes separating (110) a Fischer-Tropsch wax (124) into at least a lighter fraction (126, 128) and a heavier fraction (130), hydrocracking (120) the heavier fraction (130) to provide a cracked intermediate (144), and separating (122) the cracked intermediate (144) into at least a naphtha fraction (148), a heavier than naphtha paraffinic distillate fraction (150) suitable for use as or conversion to oilfield hydrocarbons, and a bottoms fraction (152) which is heavier than the paraffinic distillate fraction (150).