Sustainable establishment of gas warehouse requires sophisticated pump communication

Here, large amounts of water are required to wash out a salt dome near the coast of the Atlantic Ocean to make room to store natural gas imported from Algeria via a pipeline. The water, however, must be obtained in a sustainable manner from a thin vein of water located in a layer of fine, loose quartz sand, and that makes great demands on continuous control and monitoring of the entire process.

The natural gas is to be stored in five underground cavities, each more than 2 km deep and holding 1.6 million cubicmetre gas. First, however, the cavities must be created, and 600 cubicmetres of water per hour for a period of 10 years are required to wash out the salt dome – this corresponds to the water consumption of a Portuguese town with 100,000 inhabitants. At the same time, tight environmental requirements make it necessary to minimise the artificial lowering of the groundwater level caused by the water charge.

The water is collected from a depth of 21 metres via 20 bore holes drilled to a water-bearing stratum, some 8 kilometres from the future natural gas storage. The great challenge is to provide enough water without affecting the reserves in the water vein. Only water that would otherwise have streamed out at the coastline without being of use to man or nature may be pumped from the 20 bore holes that have been established along the coastline at distances of 400-700 metres from the sea.

The state-of-the-art solution from Grundfos ensures close control and coordination of pump performance. Such control is required to prevent the water level in each boring from sinking below the allowed limit, meaning that only a limited part of the water vein’s natural flow is exploited.

The solution causes minimum strain on the eco-system and has been developed by hydrogeologist Manuel João Abrunhosa on the basis of extensive measurements, analyses and tests. Quality and innovation were key to the hydrogeologist throughout the development period, and the strict requirements to security and operational reliability made him choose Grundfos as the sole supplier of pumps and equipment for protection, control and communication.

To allow automatic upwards or downwards adjustment of pump speed according to current conditions, each pump is equipped with a frequency converter. The speed of the individual pump is partly determined by the amount of water from the other borings, partly by the groundwater level in all borings. This approach guarantees a sustainable supply of the amount of water required for the washing out.

The actual groundwater level is measured using analogue probes and digital flowmeters that keep track of the amount of water coming from the individual bore holes. Grundfos PT100 sensors monitor the temperature in all the stainless steel SP pumps’ 7.5 kW motors to prevent breakdown.

The electronic signals from the bore holes are transmitted to a remote control centre that monitors all equipment, water level and flow in the 20 bore holes. Pump performance in each individual pump is continuously and automatically adjusted in accordance with the numerous data.