Application Of New Production Logging Tools To Water Production Control: A Case Study

GHOST* and DEFT*, innovative production logging tools, complemented with traditional measurements, were used for the first time in Italy in the Well Trigno 6, for water production diagnosis. The GHOST tool is able to quantitatively identify gas and hydrocarbons in multiphase flows using 4 optical sensors, measuring the refractive index of the fluid surrounding the tool. The DEFT tool can instead discriminate between water and hydrocarbons, measuring the fluid resistivity by 4 electrical sensors. Both tools have the sensors evenly spaced in the pipe cross section, and their position in space is accurately known through the use of an integrated relative bearing sensor. The individual sensor measurements are used to build an image of the downhole flow in the well. Trigno 6 (located in San Salvo gas field) is producing gas since 1967 from a sandstone multilayer reservoir; its production, facing a strong decline, was characterised by a very unstable gas flowrate (ranging from 50.000 Sm3/d to zero) and a high watercut (average water production of 7 m3/d). An intervention aimed at reducing water production was needed and the well seemed to be a good candidate as placed in a high structural position in the reservoir. Lengthening the life of this well could allow the recovery of reserves which otherwise would have remained unproduced. A production log was recorded and the image of the new production logging tools clearly identified the water entry points. A through tubing plug was set to isolate the water producing intervals. The total operating time of the above intervention was 11 hours. The intervention has turned out to be very positive as all the goals were reached: gas flow rate is now very stable and water production has significantly decreased. In addition to that, the intervention has had a pay out time of less than a month. Considering that in Italy most of the gas producing wells have typology and problems similar to Trigno 6, this innovative and cost effective solution to control water production has a relevant applicability potential.