BOREHOLE SOURCE

Objective

The project consists in developing a borehole seismic source able to work down to oil field depths (around 3000 m). It will allow the use of new borehole seismic methods (well-to-well measurements, inverse method) and will improve the knowledge of reservoir structures.
The second prototype has been surface-tested with a pressure cell simulating the borehole conditions. More than 300 shots have been achieved during the last months 1986.
The second prototype has been implemented during two tests on a test site (ELF AQUITAINE). The measuring device placed on the surface consisted in 48 traces with vertical geophones and 48 traces with horizontal geophones along the profile-traces at intervals of 20 meters that is a total length of 960 meters. During the tests performed end June good seismic signals were obtained at the surface, the source being buried between 800 m and 1100 m. The coupling device was then modified so it could be used as a confinement system : results were not satisfactory. Considering the results obtained with these prototypes, Phase 2 began with the study of a system including a weigth drop and a hydraulic coupling device; this source connected to the surface via a logging wire is a synthesis of both prototypes. The prototype willbe available in March 1988. A first version of the weight drop prototype and hydraulic coupling device has been built and developed during the first semester. A first seismic test between 2 wells distant of 550 m at depths ranging between 150 m and 450 m has been run end June with recording on a well streamer.
Two other test were completed in July and December 1988. During the last one 1500 shots were performed in 2 boreholes at depths ranging from 400 m to 500 m. Records were obtained with a borehole geophone, a well streamer in two other boreholes and a surface display. This first version is now available for industrial jobs. The processing performed on the results of the December 1988 operation produced excellent seismic survey results between wells. The emission spectrum reached frequencies of 400 Hz.
This version was also used in an April 1989 during a transposed seismic survey test in a cased well, at depths between 850 and 950 meters. Initial results indicate a fairly lowseismic energy on a surface spread, but this experiment should be repeated. The final version of the source has been improved during 1989. It was implemented during a transposed seismic survey test in October 1989 in a well of a depth of over 1200 m. An other transposed seismic test run in December implied a surface device including 6 seismic lines and 286 traces. Approximately 700 shots were made with the borehole source between depths of 200 and 300 meters.
A calibration site has been equipped in 1989 in a granitic rock.
The project is to be developed in three phases:
PHASE 1 - Theoretical prototypes
Two theoretical prototypes have been built:
- the first one uses a drill string to lift a weight which is released by the triggering signal and drops on a striking surface equipped with a suitable damper. The potential energy can be changed by changing the weight (2000 or 3000 J). The coupling of the source with the wall is provided by a packer.
- the second one uses a conventional logging cable with seven conductors to transmit energy from the surface to the tool. It uses the mud pressure to actuate a mobile system and can be adapted to work as an implosion source or a mechanical impact source. A large-surface hydraulically driven clamping system has been developed to insure the best coupling conditions. The potential energy is about 2000 J at a 1000 m depth.
PHASE 2 - Design and construction of prototype. This phase started end 1987.
PHASE 3 - Testing on the well. This phase is scheduled to start during the second term of 1988.

Programme(s)

ENG-HYDROCARB 2C - Programme (EEC) of support for technological development in the hydrocarbons sector, 1986-1989

Topic(s)

1.4 - GEOPHYSICS AND PROSPECTING

Call for proposal

Data not available

Funding Scheme

DEM - Demonstration contracts

Coordinator

GERTH

EU contribution

No data

Address

232 AV. NAPOLEON BONAPARTE
92500 Rueil Malmaison
France

Total cost