California Oil, Gas, and Groundwater Program

Digitization and Mining of Public Oil Well Records

Information on this page from Shimabukuro, David, pers. comm.

A key component the COGG Program is to make effective use of existing information, and in particular the archived information on oil and gas wells managed by the DOGGR in the California Department of Conservation. This page describes the type of information contained in DOGGR’s well archives and how the COGG Program is digitizing portions of that archive, and how that information is being used in interpretive reports.

Information Contained in Oil Well Records

There are hundreds of thousands of oil and gas well records in California.

Screenshot from DOGGR Well Finder showing location of some of the ~140,000 well records in Kern County, California.

Well Construction

The well records contain detailed information about the drilling process, well construction, and abandonment process. This includes the depths of different kinds of casing cement pumped into the annulus, and perforations.

Records also describe the abandonment process and configuration of what was left in the hole. Typically, this involves multiple cement plugs inside the casing, filling sections with drilling mud, and cutting and capping the pipe below land surface. Before the 1960s, it was not uncommon for operators to pull casing pipe out of the hole, make extensive use of mud and minimal use of concrete, and sometimes insert redwood plugs; while not summarized, many examples of these practices can be found in Summary of Operations annual reports Division of Oil and Gas, 1917-1973. As more modern techniques came into use and more stringent abandonment requirements put in place, the abandonment process shifted towards keeping the casing structure intact and using extensive amounts of cement. In some early cases, exploratory and non-producing oil wells were plugged and transferred as water wells to landowners and water suppliers.

A robust quantitative and spatial description of oil-well construction patterns is not possible without a significant investment in digitizing these records; however, COGG is recording well construction information for oil wells within a 500-meter (1,640-foot) radius from every sampling location.

Example of how data mining activities are compiling and graphic oil well casing and perforations; wells are graphed by depths and construction information. In this case, red indicates perforated intervals, green is plugged intervals, and gray is neither perforated nor plugged. This type of graphic display, when compiled for specific wells in a specific area, can help identify patterns where uncontrolled well bore flow might occur.
Typewritten oil well construction log from 1989
Example of initial well construction for a single oil well.
DOGGR Well Finder
Drawing of oil well construction
Example oil well construction data.
DOGGR Well Finder
Diagram of the construction of an oil well
Example oil well construction data.
DOGGR Well Finder

Geological Data

During the drilling process, cores and drill cuttings are collected at intervals and used to identify the depth of different formations and layer structures.

Typewritten drillers log
Example driller log with basic notes on formation properties.
DOGGR Well Finder
Typewritten drillers log from 1951
Example driller log with detailed notes on formation properties.
DOGGR Well Finder

Geophysical Data

Well records also contain geophysical logs run at the time the well was drilled.

Photocopied geophysical log
Example geophysical log from 1950s.
DOGGR Well Finder
Platform express log
Example platform express log, 2013.
DOGGR Well Finder
Example mud log from 1975
Example of mud log, 1975
DOGGR Well Finder
Scanned image of cement bond log
Example of cement bond log, 1982.
DOGGR Well Finder

Fluid Level/ Pressure Data

The State requires annual inspections of idle wells and information on fluid levels in them. These and other recorded fluid data can be compared to groundwater elevations from the same time frame to determine if there are vertical pressure differences between groundwater aquifers and oil development zones consistent with upward or downward water movement.

Extracting Information from Well Log Library

The first step in mining information contained in this well record is to create metadata that describes what information is in the well record, such as drilled depth, spud date, and what kind of geophysical logs are in the file.

Screenshot of COGG datasheet for oil well metadata.

Once the metadata are available, scientists can then identify the specific well records containing additional information for various interpretive tasks as outlined in the graphic below. For example, well construction data and water quality data are used both to create a compilation of water quality information and support regional analyses.

This graphic shows how information flows from the oil well record mining work to interpretive work.
Sources of figures portrayed above: (a) Screenshots from DOGGR Well Finder; (b) Metzger and Landon, 2018; (c) Davis and others, 2018; (d) Gillespie and others, 2017; (e) Wright and others, 2018.

COGG Progress Digitizing Oil Well Records

To date, CSUS and USGS have digitized the following information from the DOGGR well archives:

Example of digitized oil well record