Annulus pressure is an important key to maintaining Well Integrity. During the start-up of Saudi Arabia’s first offshore non- associated gas field containing high pressure high rate sour gas wells, a continuous increase of some annuli pressures was experienced despite the fact that these annuli were cemented to surface. During any well production, the heat transfer from the produced fluid to the trapped annuli fluids causes annuli pressures to increase to levels that could exceed collapse and/or burst pressure limits of the casings. This is especially true during early startup of the well when all annuli fluids are cold (offshore wells) or at ambient temperature (Onshore wells). To ensure that the pressures does not exceed the maximum allowable limit of well tubular various calculations were performed, taking into account not only the tubular limitations but also the formation pressures these casings encountered, to set the maximum limit. Periodic bleeding of pressures and continuous monitoring was necessary to avoid reaching this maximum set limit for the first four months of production. In this paper performance of the different annuli is analyzed and discussed. Calculation methods are also discussed in details which were employed to determine the maximum allowable pressure limit for each annulus. Elimination of frequent bleeding of 1st casing-casing annulus in one of the wells by revisiting the maximum limit, taking into consideration the formation pressure the casing was set in are some of the lessons learned documented during this first offshore gas field startup and will be put forth in the paper.
展开▼
