RIASSUNTO
SPE Members
Abstract
A new, slimline, fully-retrievable, Directional MWD tool (DMWD), is finding new applications for and benefits from MWD. Case histories illustrate how compact size and full retrievability are extending MWD into areas of high stuck-pipe risk, small holes, high-temperature drilling, low-budget wells, and remote locations.
Introduction
Development of a small, low-cost, wireline-retrievable measurement-while-drilling (MWD) system began in 1981. Every effort was made to maintain full retrievability, as a number of significant benefits and applications were recognized as being achievable.
Within the past year, the DMWD tool has been operating in the U.S. in a wide range of drilling environments, in both typical and new applications. The tool has provided MWD in wells where conventional MWD systems were impractical.
DMWD tool description
The final design of the tool had to meet four key requirements.
*The entire tool had to be fully retrievable to ensure the operating oil company a minimal MWD-lost-in-hole risk.
*One size tool had to operate in all sizes of drill collars, to maintain flexibility and simplicity of use.
*The tool should have the lowest weight possible for high portability, including helicopter transport.
*The addition of other drilling hardware to the drillstring (e.g. MWD pulser subs, high-cost customized MWD drill collars) should be eliminated.
Areas avoided in its design included complexity, size, and high cost. The result, after extensive field testing, was a tool with the following specifications:
DMWD OD, in. (max) 2 (51mm) DMWD length, ft (min) 23 (7 m) (max) No restrictions, length matches drill collar Total weight, lb(typical) 175-200 (80-91kg) Assembled from four 4 to 7-ft modules
Other specifications are shown in Table 1.
The tool is shown in Fig. 1.
Full retrievability achieved. The tool passed freely each way through drillstrings with IDs of 2 1/4 in. or larger. A fishing neck is placed on the very top of the pulser to permit wireline retrieval.
Extensive wireline retrieval testing was performed with different depths, hole angles, mud weights, drilling assemblies, and wireline retrieval equipment comprising the major areas of research. Results showed that the tool could be removed effectively whenever necessary, by using the appropriate wireline equipment for the prevailing conditions. Any wireline of 0.092 in. or larger outside diameter (OD) may be used. It is even possible to simultaneously retrieve a single shot and DMWD, for example, at TD prior to conditioning mud and running logs (when the tool no longer is required) or when replacing a tool.
One size tool achieved. The tool can be located in standard non-magnetic drill collars with the following specifications:
OD, in. (minimum to date) 4 3/4 (maximum to date) 10 ID, in. minimum 2 1/4 typical 2 13/16 Connections No restrictions BHA placement No restrictions Stabilization No restrictions ""MWD"" collar OD/hole size No restrictions Weight on bit (WOB) No restrictions Rotation (rpm) No restrictions
P. 87^