Possible Problems And Solutions For Shallow Testing Of MWD Instruments

Measurement While Driling (MWD) is an advanced technique used in directional drilling to measure certain information near the bottom of the bit hole without interruption and to transmit the information immediately to the surface.

As one of the Measurement While Drilling products,Small Diameter Measurement While Drilling (MWD-Φ38mm) is a kind of small-path mud pulse wireless in-drilling inclinometer. This product not only has the high precision, high stability and high vibration resistance, but also has a wider range of applications.ER-MWD-38 Measurement While Drilling can be used for the construction of conventional wellbore .Different diameters can be selected according to the conditions of on-site drilling tools (diameter of the drill collar Ф50.8mm, Ф71.4mm) Rubber wings to suit different drilling tools.

MWD wireless inclinometer working anomaly usually manifests in two forms, one is the dominant fault, the other is the hidden fault. The so-called apparent fault is the factor that causes the abnormal operation of the instrument, which can be directly tested and found through the detection of signal generators and multi-function meters. This kind of fault phenomenon is characterized by obvious fault points and easy to deal with. The hidden fault is that the inclinometer components have a long life and a long service time, and the performance of some executive components such as the precision sensor and processing circuit in the probe tube and the capacitive section of the pulse generator decreases under the condition of high temperature and high pressure at the bottom of the hole, resulting in the abnormal work of the downhole instrument assembly. The fault is characterized by the strong concealability of the fault point and is not easy to judge. If the instrument operator has mastered a certain professional basic knowledge, the following methods can be used to judge the abnormal work of the instrument during site construction.

Intuitive method: Directly observe the degree of use of vulnerable parts, make a preliminary judgment and replace the parts. There is also the use of MWD special testing instruments for standard testing of instrument assembly components during base maintenance, to ensure that the performance indicators of drilling instruments meet the requirements, and to replace and repair the faulty parts.
Reasoning method: Each part of the downhole instrument assembly is updated one by one, and then the connection is routed into the well to test its performance until the instrument works normally.

Phenomenon: The shallow test of the instrument is normal. After working for a period of time in the well, the signal is getting weaker.


1: The sensor is blocked.

2: Mud displacement exceeds the normal range of variation.

3: The viscosity of the mud becomes larger or the specific gravity becomes smaller.

4: The pump pressure is reduced.

5: The rotor eccentric wear speed is reduced.

6: The pulser telescopic sleeve becomes larger due to the high temperature.

7: The outer diameter of the mushroom head becomes smaller or the inner diameter of the restrictor ring becomes larger.

8: Fall into foreign bodies.

9: The filter block pump pressure rises.

10: The temperature at the bottom of the well exceeds the standard, causing the probe or pulse generator to not work properly.


1: Replace the pressure sensor.

2: Adjust the displacement.

3: Treat the mud and reduce the viscosity.

4: Large-scale activity drilling tools.

5: Replace the downhole equipment.

6: Repair the mud pump.

7: Replace the probe if the bottom hole temperature is too high.

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