Halite salt deposition in the near wellbore formation and the wellbore of a gas well can dramatically reduce its productivity within a very short period of time. In order to minimise the salt induced formation damage, it is essential to identify if, where and how much halite will be deposited. The main objective of this work is to develop an easy- to-use tool for downhole salt deposition risk assessment and management.

The main mechanism for halite deposition in the near wellbore formation and the wellbore of a gas producer is water evaporation at a reduced pressure. A high deposition risk is expected at a high drawdown and a low produced formation water to gas ratio (FWGR). Halite deposition can also occur at a reduced temperature or pressure due to reduced halite solubility in water. A halite envelope can be used to determine the downhole halite deposition risk, which is a boundary marker for the start of halite deposition at which point halite is saturated in water. Two types of halite envelopes are introduced in this paper. One is for different reservoir pressures at differing FWGRs and but at a fixed temperature. The second is for different temperatures at differing FWGRs at a given reservoir pressure.

A number of North Sea gas field halite deposition cases will be presented in this paper. Each case will illustrate how the halite envelope technique can be used to identify high risk wells; their salt free operating conditions or to determine the requirement for water washes, and their associated injected water volumes. It will also demonstrate that for its successful application, reliable measurement of the water and gas production, along with an understanding of the water/gas influx, are both prerequisites in the validation of a halite envelope.

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