Browse Prior Art Database

A Robust Mud Pulse Telemetry System for Error Prone Mud Channel

IP.com Disclosure Number: IPCOM000244900D
Publication Date: 2016-Jan-27
Document File: 7 page(s) / 506K

Publishing Venue

The IP.com Prior Art Database

Abstract

Drilling holes for exploration and production of oil and gas is a business. In order to gather information on the hydrocarbon reservoir and optimize the placement of the borehole, the bottom hole assembly (BHA) at the lower end of the drillstring is instrumented with sensors that take various measurements to conclude on the properties of the rock surrounding the borehole (resistivity, natural gamma radiation, etc.). This information is transmitted to the surface where critical decisions are derived regarding the drilling operation. The most common communication channel is the drilling fluid inside the drillpipe. The transmitter sends a modulated pressure signal propagating through the fluid in the drillpipe. Signals from various noise sources downhole and at surface interfere with the telemetry signal. This publication discloses enhancements for the Mud Pulse Telemetry System through the usage of a soft decision decoder. Different modulation approaches are included in this publication, which achieve different data rates for a specific error rate based on the channel frequency spectrum. Channel coding with soft decision decoding is used with these modulation schemes, to reduce error rates compared to hard decision approaches.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 27% of the total text.

Page 01 of 7

Title:

A Robust Mud Pulse Telemetry System for Error Prone Mud Channel

Abstract:

Drilling holes for exploration and production of oil and gas is a business. In order to gather information on the hydrocarbon reservoir and optimize the placement of the borehole, the bottom hole assembly (BHA) at the lower end of the drillstring is instrumented with sensors that take various measurements to conclude on the properties of the rock surrounding the borehole (resistivity, natural gamma radiation, etc.). This information is transmitted to the surface where critical decisions are derived regarding the drilling operation.

The most common communication channel is the drilling fluid inside the drillpipe. The transmitter sends a modulated pressure signal propagating through the fluid in the drillpipe. Signals from various noise sources downhole and at surface interfere with the telemetry signal.

This publication discloses enhancements for the Mud Pulse Telemetry System through the usage of a soft decision decoder. Different modulation approaches are included in this publication, which achieve different data rates for a specific error rate based on the channel frequency spectrum. Channel coding with soft decision decoding is used with these modulation schemes, to reduce error rates compared to hard decision approaches.

Description:

This publication considers the pulse code modulation approach, where two different line codes are depicted; Manchester and Miller line codes. The main idea is to apply these line codes in combination with forward error correction and soft decision decoding in the receiver design, as shown in figure1. The usage of different line codes or the usage of soft decision decoding is mentioned in the literature but not together.

Figure 1: Communication System for Pulse Code Modulation


Page 02 of 7

For Manchester and Miller codes, an interleaver can also be added to the system to reduce the impact of burst transmission errors on decoding error rate.

The following combinations are proposed for use in the context of mud pulse

telemetry:

1. Manchester line code + convolutional FEC code + soft decision decoding 2. Manchester line code + convolutional FEC code + interleaver + soft decision decoding
3. Miller line code + convolutional FEC code + soft decision decoding.

4. Miller line code + convolutional FEC code + interleaver + soft decision decoding

Detailed Description:

In this section, each block in figure 1 will be explained in more detail.

Figure 2: Manchester and Miller Line Codes for a Specific Bit-Stream [1]

The two line codes are shown in figure 2 for the same bit-stream, where we can notice that Manchester code has more transitions than Miller code. Manchester code has a specific bit shape for each bit value: zero or one; accordingly, level transitions occur at every bit. Miller code has four different bit shapes; two bit shapes for each bit value ('0', and '1'), as explained in [1]. Miller code is also known in literature...