Objetivo
The development of a tool to improve the maintenance of a constant oil supply from offshore pipelines implying the need for an early detection of small leakages. The early warning of accidentally occurred cracks in the pipeline would improve the operational security and thus minimize the risk of sudden production stops.
Traditional methods such as the registration of the pressure above the pipeline are not sufficient for the detection of small leakages, whereas the determination of the content and type of hydrocarbons in the water along the pipeline is be a valuable tool. 1st generation fluorimeters may detect oil in water, but apart from this it is important to be able to ascertain whether the oil detected originates from the pipeline. Moreover, the sensitivity of the fluorimeters should be improved.
A) ACOUSTICS
- HARDWARE
The final design of the complete data acquisition system has been finished. e can now perform fast measurements with 32 transducers.
- MODELLING DIFFRACTION
A package has been written to be used as a forward elastic modelling tool for prediction of the wavefield observed during the hydraulic fracturing experiments. The code is based on the finite difference solution of a full elastic wave equation. The program offers the possibility to analyse and view wave propagation effects for very complicated model geometries for which solution with other modelling methods is difficult to obtain.
B) MODEL TEST
- REORIENTATION TEST WITH VARIATION OF SEVERAL PARAMETERS
Until now, 60 model tests were carried out for various wellbore orientations.
The influence of the following parameters on the fracturing process has been investigated :
- Cementing the casing in the borehole : we found that previous experiments with the liner cast in the block gave a different fracture geometry
- Fluid rheology and injection rate : initiation of fractures was found to governed by fluid flow; rather than tensile breakdown.
- RELATION MODEL TO FIELD APPLICATION
A field study of hydraulic fracturing in horizontal wells in a North Sea tight chalk oil-gas field was complemented. It was found from simulations with FRACPRO (fracture simulator developed by the US Gas research Institute) that during the treatments a large part of the fracturing pressue came from near-wellbore friction. Furthermore the cause was determined of communication problems in this field between fracture and wellbore.
The fluorescence spectra of different oil in water are not especially specific for the single type of oil, but if we also take into account the lifetime curves along the spectrum, forming a 3-dimensional spectrum, specific information on the type of oil being measured can be obtained. The project is therefore divided into two main phases :
Phase A :
Development of a 2nd generation prototype fluorimeter basd on laser-induced single shot fluorescence. The exitation wavelength should be tuneable due to the use of a frequency doubler in cooperation with a color dye laser pumped by a nitrogen-laser. The fluorescence should be measured simultaneously in 35 channels forming a spectrum covering the wavelengths from 250 nm to 660 nm, and having a channel width of 10 nm.
Phase B :
Development of a 3rd generation prototype fluorimeter based on the 2nd generation fluorimeter, but including the measurement of lifetime-curves in each channel, thus forming a 3-dimensional spectra. This techniqueshould be called laser-induced single-shot fluorescence lifetime spectroscopy, and the developed prototype should be tested and used as the basis for industrial production of an in-situ 3rd generation fluorimeter.
Each of the two main phases is divided into a number of stages as follows :
A1- Collection of existing knowledge concerning UVF-technology, lasers and optical fibres. Specification of a 2nd generation system to be build in the laboratory (wavelength, energy-requirement, transmission losses in fibres, fibre types etc. . ).
A2- Construction of the first laboratory prototype model of the instrument (one channel only). The model will be constructed in an optical bench at the Institute of Physics (University of Aarhus).
A3- Optimization and testing of the laboratory prototype model will be performed using samples of pure hydrocarbons. The optical parts of all 35 channels being tested in the model channel.
A4- Construction of a final prototype of the 2nd generation fluorimeter including all 35 channels.
B1- Development of very fast detection electronics, (sampling time less than 10 ns) which should be tested in the model channel and then miniaturised for use in all 35 channels.
B2- Development of a micro-computer system for control of the laser and collection and storage of the fluorescence lifetime curves from the model channel.
B3- Reconstruction of the 2nd generation prototype to form the final 3rd generation prototype including all 35 channels.
B4- Optimization and testing of the 3rd generation prototype fluorimeter using standard oils mixtures etc. . in seawater.
Programa(s)
Tema(s)
Convocatoria de propuestas
Data not availableRégimen de financiación
DEM - Demonstration contractsCoordinador
8000 Aarhus
Dinamarca