Objective
The purpose of drilling a borehole is to acquire better knowledge of geological formations crossed and to ensure production under the best performance and safety conditions, taking time and cost into account. A major part of this gain can be obtained by full control, at all times. of essential drilling parameters (bed and surface), so as to enable their interpretation, correlation and, from this, optimization of all drilling operations. These operations could then be automated, to a varying degree depending on the local contraints, using softwares or even artificial intelligence.
In order to pinpoint the various activities envisaged in this project, the work program has been broken down into three main technological areas :
- DRILLING MEASUREMENTS.
- DRILLING HYDRAULICS.
- TRAJECTORY CONTROL.
a) Drilling measurement
Detailed studies of systems ALSGEO (GEOSERVICE), GEMDAS (EXLOG) AND ADVISOR (ANADRILL) revealed the unsufficiency of some of the systems as to the representation of data in real time (penetration speed, gas shows. . . ), the little progress of sensors (flow of mud inlet and outlet) and the variable performances of degassers. On the other hand, these systems offer the possibility of replaying the logs, the creation of databases, a follow-up in real time, the connection with work stations and the integration of mud -logging measurements and of MWD measurements.
A report on MWD state of art shows that MWD service companies are generally capable of running measures of good quality comparable to those made by wireline.
Thanks to the development of mud-logging data softwares it is now possible in connection with new systems to automatically process mud-logging and MWD data depending on the depth and soon on the time.
Interpretation of quantitative and qualitativemeasurements is blocked by the poor efficiency of degassers. Methods for evaluating the formation pressure and porosity are faced with two problems : the unaccuracy of drillability and bit wear formula and the consideration of lithology in computing models.
On site tests for setting up bit wear criteria during drilling were run on a single well and under difficult operating conditions. These tests have not allowed to validate the interpretation method. Operating conditions were reviewed and will be implemented in the future.
b) Drilling hydraulics
A computing link (meshing of bit and borehole, post processor for presenting results) has been set up for studying hydraulics at bit and stabilizer level. This link has been validated for a simple geometry tool thanks to tests carried out on the two envisaged benches. These tests showed that modelling could be simplified. Concerning the cleaning of the well and use of hydraulic power, priority was given to the computing of pressure drops in the drilling fluid circuit and the computing of annular pressures during operations. The validity of the numerical program without hypothesis on the rheological model has been checked in the case of wells drilled with water-based fluids, or a shallow depths with oil -based fluids. Calibration and validation of the software for oil based fluids at important depth will be performed on a test prepared on a real well and which will be run during phase II.
The study of hydraulics at the drill front has implied the development of a software simulating flows in the bit area, with the help of a reservoir flow model. The influence of the pressure distribution in the sub-jacent block on the bit penetration speed will be determined thanks to experiments run on the drilling bench.
c) Control of trajectory
Requirements were analysed in the form of a survey. This survey shows the need for a friction computing software and a previsional trajectory calculation software.
a) DRILLING MEASUREMENT
- The evaluation of the current state of the art for mud-logging techniques and measurement while drilling (MWD) will be given in reports relating to the services offered by this new generation of measurement facilities proposed by the contractors.
- Elaboration of graphic measurement softwares, written processing and automatic comparison with data from other sources, mainly the wireline.
- Feasibility study of measurement operating methods, aimed at characterizing formation fluids through gas index measurement. Feasibility study of a parameter calculation method for formation ( permeability, porosity, drillability, pore pressure). The initial step will be a critical study of the products offered by the contractors in this field.
- Feasibility study for the drafting of a PDC-and three-cone-rock bit wear law that is reliable and covers a wide field of applications. This study will be based on a limited study of bed wear and a detailed phenomenological analysis.
b) DRILLING HYDRAULICS
The studies, development works and test setup and on-site experiments under real operatintg conditions should lead to :
- the improvement of tools and bottomhole equipment and optimization of their use. The hydraulic flow studies and tests carried out on test setups will make it possible to ask equipment manufacturers to modify their products and increase their performances, efficiency and service life. As regards drilling tools, special attention will be given to tools with synthetic -diamond blades (PDC).
- operational procedures and methods making it possible to make, on site, the best selection of hydraulic parameters, in function of conditions encountered, and to define the specifications best adapted to the drilling fluid.
- decision-making softwares enabling the site manager to modify and control hydraulic and mechanical drilling parameters and drilling fluid rheological characteristics, as a function of the measurements made while drilling and the condition of the well.
c) CONTROL OF TRAJECTORY
- An analysis and definition of requirements will be provided for trajectory selection.
It is already known that a "friction" software should be developed. If this analysis shows that there is a need for other softwares, their feasibility will be evaluated. The general analysis of the "friction" software and the special software will be carried out during phase 1 and up to completion time (probably without validation during this phase).
- As regards trajectory selection, the following will be provided :. a general analysis of a software simulating the behaviour of a packing with a deflection tool (bent stub or offset stabilization) and, if possible, the elaboration of the software (probably without validation during phase 1),. the statistical analysis of the azimuth behaviour of the bottomhole assembly, depending on the formation dip,. results on digital model validation using the microdrilling test bench.
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DEM - Demonstration contractsCoordinator
92500 Rueil Malmaison
France