Several Indonesian gas fields such as the Tunu field exhibit a specific behavior which causes a rapid decrease of the gas production. At shut in conditions, cross-flows from watered out layers to gas producing layers, were clearly identified as the major cause for gas production impairment.

The offloading of water from wells is performed at the preliminary stage of water production and often allows restarting the wells, but in a second stage it is ineffective. The nature of the damage in the gas-producing zones is not entirely understood but it seems to be a combination of at least two phenomena: (i) water adsorption on the high amount of clays present in these highly water sensitive layers (15 to 40 wt %) and (ii) water imbibition due to some capillary pressure experienced in the tightest layers (0.1 to 10 mD). Clay swelling or migration seems also to contribute for this damage but to a lesser extent.

Unwanted water along with gas and condensate production from several layers were quantified from multi-rate PLT, to define a strategy for well candidate selection and water shut off interventions. An inorganic gel was then selected to be selectively squeezed into the water-producing layers. The optimization of this fluid and of the preflush fluid required a complete qualification program which aimed at three main objectives: (a) maintain injectivity during the squeeze to allow an entire placement of the fluid, (b) provide, once set an extrusion pressure sufficient to withstand a significant drawdown and (c) gives a treatment's lifetime of one year minimum.

Three wells were treated in 2004, following the qualification of the fluids, the selection of candidate wells and the implementation of a complete treatment setup on a barge. This article describes the successes and the failures of some of them, pointing out the need for finely filtered fluids, low viscosity fluids and robust selective placement tools.

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