Objective
The objective of the project was to develop the prototype of an existing microwave PVT apparatus into a commercial product. The principle that is exploited in this project is the change in dielectric properties of a hydrocarbon mixture when the state of the mixture changes from one to two phases. This can be very difficult for certain fluids (near critical) with existing methods. Two other strong features of the apparatus are the fact that is is mercury free and that it is very compact. It is designed to be transportable making it useful for field applications. The small size of the apparatus results in the benefit of using very small fluid samples (40 cc).
A transportable mercury free, high pressure PVT apparatus has been developed. The working range is 40-50 deg. C and 0-500 bar. The sample volume is 40 cc. It is considered particularly useful for sample validation and saturation pressure measurements in the field. The small sample volume is desirable due to the normally limited amount of sample available.
The saturation pressure is detected by the change in the microwave resonance in the sample when the new phase is formed. In contrast to the prototype developed by KT in an earlier research project the sample is now placed in the resonator. The volume of the resonator is kept constant during the expansion of the sample. Mechanical stirring inside the cell reduced the equilibration time at new conditions. The cell is placed in a thermostated air bath. The air bath is at the same time the box in which the cell is transported. The motor controlling the piston in the cell is placed outside the air bath. It can be detached and is transported in another box together with the electronic parts.
The transportability of the apparatus was demonstrated by the fact that from arrival at Wytch Farm the apparatus was in operation within 30 minutes. Oil and gas samples were studied with good results. By courtesy of the service company Expro it was possible to extend the proving test at their facilities. Here additional reservoir fluids from other reservoirs were studied. It was in particular interesting that it was easy to measure the saturation pressure of a near critical fluid. This is by conventional methods extremely difficult. The apparatus is being commercialised by co-contractor ROP, which has included it in its product line.
The project was divided into five phases : 1) Theoretical development of design and improvements from prototype. 2) Design of cell and test of different detection methods. 3) Construction of the apparatus. 4) Laboratory testing of the new apparatus. 5) Proving test with reservoir fluids and field test. From the beginning the roles of the different partners were very clear. The idea and the existing prototype belonged to Institut for Kemiteknik (KT). Here the research and development environment was present to carry out the further development of the detection principles. BP had the need, the knowledge about specifications, could provide samples, and finally a location for a field test. ROP has along experience in designing and constructing mercury free, high pressure PVT equipment for the petroleum industry. General project meetings were held at regular intervals of 6 to 8 months, depending of the need. The theoretical development was carried out at KT in collaboration with BP. Aphysicist was employed at KT to make proper development of the microwave part. Some fundamental improvements were made compared to the original prototype. The detailed design of the apparatus itself was then made by the company ROP which has specialized in developing mercury free high pressure equipment. Several different detection principles were tested in order to optimize the analytical accuracy. A sound theoretical interpretation of the different detection principles made it possible to find the most suitable of the available options. A fixed resonance volume containing the sample was finally chosen. The construction was made by ROP based on the design from phase 2 and technical specifications concerning safety and other requirements defined by the conditions at the well site. These were provided by BP. The apparatus was delivered on time and the mechanical, electrical, and control software was in accordance with the specifications. After the design phase at KT was finished the time was used for software development for the microwave analysis while the construction took place at ROP.
The apparatus was tested in the laboratories of KT. Boiling points of pure substances and bubble and dew points of binary mixtures were used to test the apparatus. Since both the control software of ROP and the microwave analysis software were written for Windows it was as planned easy in practice to integrate the two with a interface written in Visual Basic. Good accuracy was obtained for the well-defined systems.
The first part of the proving test consisted of measuring the dew and bubble points of some fluids provided by BP. This included a synthetic gas condensate mixture, a separator gas, a gas condensate, and an oil. The second part of the proving test took place at the Wytch Farm oil field in Southern England. This field is operated by BP and samples taken on site were used to test the apparatus.
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DEM - Demonstration contractsCoordinator
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