Paper: Use Of Automated Logging Units For Predicting Abnormally Pressured Formations And Well Correlation

Recent field tests in South Louisiana have culminated a three-year research project by Baroid. The project objective was to apply the computer expertise developed while producing Baroid's CDC (Computerized Drilling Control) units introduced in 19711 to the development of an automatic pore pressure logging system. The CDC units require crews of up to seven people. The proposed system was to require only three crew members through more reliance on the computer for data collection, analysis, and presentation. The system (now designated Automatic Logging Service - ALS) evolved through several distinctive developmental phases. The first was the theoretical phase in which a mathematical model of the drilling operation was developed. This phase was reported by Bourgoyne and Young in 1973.2 The second phase consisted of field-testing the model through use of electronic calculators at the well site. The third phase was to implement the model in software for a mini-computer designed for real-time operation. The fourth and recently completed phase was to field-test the complete equipment and software package system. The ALS unit is designed to use a modern digital mini-computer, sensor devices, a system of mathematical equations, and one operator per tour to produce a pore pressure log on a continuous basis while drilling. Computer system responsibilities include data monitoring, storage, analysis, and presentation. Data collection is accomplished through the use of rig-mounted transducers that monitor the drilling parameters and transmit analog signals to conditioning panels. These panels then convert the transducer outputs into computer compatible signals. The computer reads and scales these values into engineering units. Parameters being automatically monitored are depth, hook load/bit weight, rotary speed, pump strokes per minute, on/off bottom, catalytic mud gas, and thermal mud gas. Parameters manually entered into the computer are mud density, shale density, sand/shale percent, and pertinent wellbore constants. Drilling data storage is accomplished through the use of a magnetic cassette tape unit that is fed from the computer on a time and event basis. Events that cause tape records to be generated are: the beginning of a bit run, the end of a bit run, the completion of a drilling interval, and the completion of a lag interval. During drilling, data averages are accumulated until an interval is completed. These averages are then stored on the tape. Records are created of certain data lag arrays on a time basis to minimize loss due to power failure. These lag arrays are dumped onto tape every 15 minutes. The system recovery program, following a power outage, automatically reads the most current lag array record into memory. The format of the stored data permits easy on-site utilization. Data analysis is done by applying the drilling model and drilling response equations. Drill rate is computed from the depth and on-bottom signals for several interval sizes (1, 2, 5, and 10 feet)