The basics still count when it comes to well data collection—and the methods used to obtain it.
For downhole information, operators overwhelmingly employ wireline logging, a long-time industry staple that produces high-volume descriptive data that can be compared against a large library of existing logs and interpretive knowledge. Wireline logs prove especially useful when operators are delineating new acreage.
The largest proportion of wireline data collection still involves the tried-and-true triple-combo log, which provides information on density, porosity and resistivity—the holy trinity of downhole data. The main advantage to the triple-combo is the ability to string together different logging tools in a customized manner and convey the tool assembly through the drillstring.
Operators employ a number of variations, including quad-combo and through-the-bit logging services, with the latter used to overcome conveyance obstacles associated with making the curve and performing successfully in horizontal laterals. Through-the-bit logging tools reduce the cycle time for logging because of quick conveyance through the drillstring and deployment from the end of a pass-through drillbit. Drillers maintain full surface pressure control during the process.
Hart Energy’s Market Intelligence program surveyed participants in the downhole data collection business, including operators, seismic and wireline providers, and consultants, in December 2014. The surveys had a Permian Basin bias, though conversations were held with participants active in multiple plays across the domestic market.
Nearly 80% of those using wireline logging employ the practice openhole as opposed to cased-hole logging. In some cases such as horizontal laterals, operators run a single tool to collect openhole gamma rays. Otherwise, operators restrict data collection to the vertical column of the well.
The progression of logging services in a drilling program ranges from use in all pilot holes while delineating a play to a sample of holes in the vertical section of wells in close proximity when an operator reaches resource development mode.
Less frequently used data acquisition techniques include sidewall coring, chemical or radioactive tracers, 3-D seismic and microseismic. Microseismic data are rising in use, though the technique still has low market penetration. Microseismic is used to monitor the progress of completions and provide operators an opportunity to tweak completions to enhance productivity.
Now that the land grab is behind the industry, operators are joining together in best practices. Operators generally will share area 3-D seismic information during the resource development phase of unconventional plays. These data also are seeing greater use in reservoir characterization.
Cost is the most common issue involved in the decision to collect downhole data. Participants in the Hart Energy survey noted basic downhole data acquisition added about 1% to well cost.
“Wireline logging is still our most common data acquisition tool,” a mid-sized Texas operator told Hart Energy. “The data portion is only around $10,000 per well. Most wireline cost is for the ‘per stage’ cost for perf [perforation] guns and setting plugs. Data acquisition usually runs us less than 1% per well.”
Microseismic cost can reach $150,000 for each well monitored, though in pad drilling the cost is spread among multiple wells on a pad. Microseismic adds 3% to 4% per well to data acquisition costs.
Surprisingly, permanent downhole instrumentation remains limited in market penetration, primarily due to the expense of the process. Fiber optics used for instrumenting a wellbore can add $500,000, with no clear metrics on whether or not the investment pays for itself.
Few survey participants expect the use of downhole data to decline, even in a downturn. Operators are now looking to become more efficient with completions in a down market to maintain profitability, and downhole data are marketed as a way to add value.
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