Objective
Safety and efficiency during the hydrocarbon drilling process is critically dependent on a knowledge of the material being drilled and the hazards associated with proceeding. Unfortunately, current seismic techniques with source or receivers at the surface, including surface seismics, VSP/IVSP and TOMEX, only give a resolution of at best about 20 m.
The aim of this project is to build, test, and demonstrate a Look Ahead of the Bit system with a resolution of better than 1m and suitable for use in a real drilling scenario. The system, based on piezo-ceramic transducer technology, will be capable of detecting lithological interfaces or fluid boundaries ahead of the bottom of the borehole during the drilling process. This will be demonstrated in a typical hydrocarbon bearing rock sequence or similar. The project aims to have a service company exploit the technology following this demonstrator phase.
During the Feasability Study Phase of the DEA68 project, a non-drilling experimental device was used for experimentation down shallow boreholes at depths of up to 90m in shale and sand sequences. This proved the ability to see acoustic contrasts out to ranges in excess of 60m in front of the drill bit and to achieve high resolution of better than 1m. Data processing techniques, such as pulse compression, Auto Regressive Moving Average (ARMA) deconvolution and beamforming, improve the resolution and discrimination against unwanted signals.
Subsequent tirals on quarter-scale model in boreholes (of 120m equivalent full-size depth) verified many of the major design components and gave confidence to proceed to manufacture of the full-size Demonstrator tool.
Analysis of data collected during the Demonstrator field trials at Montrose has involved the development of a variety of further data processing algorithms for enhancing the desired signals and for suppressing unwanted and interfering signals. These algorithms are largely based on well known sonar and seismic techniques, but also include some novel approaches.
In order to assess the look-ahead performance of the Demonstrator system, the Montrose hole was continued and conventional wireline logs run in this hole in order to obtain the 'ground truth' of the lithological interfaces which the Demonstrator was attempting to detect. A comparison of the results of the data analysis with the impedance log (derived from the sonic and density logs) provided the evidence that geological interfaces were being detected at ranges to meet the design aim.
In addition, the mechanical design of the Demonstrator tool was proved to be success as the BHA held angle and survived the drilling environment without problems.
Following the raising of patents, an R&D programme demonstrated the concept of insonifying the earth ahead of a borehole by acoustically exciting a mass similar to a drill bit in close contact with the bottom of a borehole and receiving the signals in the same borehole. The results of the R&D programme are to be applied to this project to make a Technology Demonstrator of a drilling compatible system which will 'look' ahead of the drill bit. The demonstrator tool is ruggedised and integrated into a Borehole Assembly (BHA) for use with 8 1/2" PDC drilling bits. The system was manufactured in 14 months, will be tested in May and initial trials will be conducted in a non-operational borehole in June 1997. The subsequent 7 months will see minor modifications to the design, with more extensive commissioning tests.
The innovative part of the project is the design of a system based on a piezo-ceramic transducer mounted in the BHA so that controlled acoustic signals can be employed to 'look' ahead of the drill bit. The method is as follows : while drilling is paused, the transducer is actuated in order to vibrate the drill bit. With the drill bit in close contact with the bottom of the borehole the earth is acoustically excited and acoustic signals are propagated away from the borehole bottom. The signals are partially reflected at formation or fluid boundaries where there are changes in acoustic impendance, and are received on a number of transducers mounted in the BHA close to the bottom of the borehole. For the Demonstrator system, the signals will be transmitted to the surface using a retrievable wireline system, where they will be processed to enhance the visualisation of the acoustic boundaries. For a commercial system, this wireline would be replaced by conventional mud-pulser technology, with sufficient downhole data processing to compensate for the corresponding reduction in communication performance.
The R&D programme also addressed the location and types of receiving elements together with new processing techniques which are required because of the novel nature of the signals. Modified Sonar and seismic data processing algorithms have been successfully applied to the R&D data to provide processing gain, to enhance and identify signals and to discriminate wanted signals against unwanted signals and noise in the preferred look direction. In addition, a highly innovative transmit signal generation technique has been developed which takes the rock formation characteristics into account adaptively, improving the potential system resolution.
Fields of science (EuroSciVoc)
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CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques.
- natural scienceschemical sciencesorganic chemistryhydrocarbons
- social sciencessociologysocial issuessocial inequalities
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Call for proposal
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DEM - Demonstration contractsCoordinator
BA8 0DH Templecombe
United Kingdom