Thursday, August 27, 2009

Careful Drilling Needed To Produce Shale Gas

It is possible to "steer" a well while it is being drilled, "land" it exactly where desired, and keep the well drilling for thousands of feet within a thin target zone, or "sweet spot"........ and for a lot less than $100,000. I speak from experience.

NAPE: Drastic improvements needed in shale gas

By OGJ editors
HOUSTON, Aug. 26
-- Efficiency improvements of at least an order of magnitude are needed in US shale gas plays because field costs will not stay at the levels to which they have dropped since late 2008, said a speaker Aug. 26 at the Summer NAPE E&P Forum in Houston.

Now that the industry has mastered combination of horizontal drilling and multiple frac stages, the rate of technology growth seems to be slowing, said William Coates, president, Schlumberger Oilfield Services, North America. Taking more measurements in each well may be the key.

Drilling and completion capital costs are not going to stay low, and field service costs may begin to increase within a few months, said Coates.

The proliferation of frac jobs to as many as several dozen per well is inefficient, and most operators don’t take enough measurements in the vertical or horizontal portions of shale gas wells once they have completed their initial reservoir characterization drilling, he said. The move from science mode to gas manufacturing is too abrupt.

Companies should set a goal of obtaining the same ultimate recovery by “doing less,” Coates urged. They must find ways to cut the drilling time of a typical shale well to 7 days from 28, for example, by attaining the capability for a single bit run for the vertical part of the hole and one bit run for the curve and lateral.

Landing the lateral at the depth of the sweet spot at any given well location could result in twice to three times the ultimate recovery if an operator spent an extra $100,000 on measurements, Coates estimated.

Other steps toward efficiency could come in the use of friction reducers and biocides to halve the amount of water required for fracs, laying fiber optic cable outside casing to measure vibration to learn which frac stages are producing, and learning how to conduct fewer inefficient fracs by using log-while-drilling measurements to select perforated intervals.


  1. Pete, you have interpreted that sentence entirely differently than I did. My interpretation was that IF they would spend an extra hundred thousand on WELL LOGS (measurements) they could FIND the sweet spot while they were drilling. I did not interprete it to mean that it takes extra money to improve the precision of drilling. Precision is nothing if you miss the actual production zone. Staying in zone does not mean "hitting the sweet spot." More often than not I see the engineers cutting out the costs of extra logging measurements because they see them as wasted money.

  2. No, no, no, no. Drillers are told where to drill before they begin. This is called a "prospect" and it is used to "sell" management and investors on an idea. It must be very convincing also. Nobody, except our government, throws money around without a lot of thought.

    In the case of "shale gas", people use a vertical well, (think of this as a conventional well) with normal logging, coring and testing done as a standard. They use this to identify where a "sweet spot" is in stratigraphic terms. This has little to do with structure, or how "high" the rock layer is. Conventional seismic interpretation is at a loss here. This is truly in the realm of the sedimentary, stratigraphic geologist.

    When drilling, the trick is to find and stay in that pre-determined stratigraphic layer. In spite of what anyone, even Schlumberger, says, they're not "sniffing" out hydrocarbons while drilling, like a hunting dog looking for a downed bird. They're looking for a particular layer of rock, whether it be a porous and permeable layer of sand, or a brittle layer of shale, or some limestone oozing hydrocarbons.

    No one can detect hydrocarbons while drilling, but they can indentify rock types. The main tool used while drilling is the Gamma Ray detector. It basically identifies the difference between "dirty" rocks, (shales) and "clean" rocks, (sands and carbonates). That is it; that is all....they're looking for rock layers, not hydrocarbons. That's my perception and opinion anyway.

  3. So-called "horizontal drilling" is a whole new ball game. Conventional wire-line logs do not work or can not be used. Put aside your fancy density, neutron, sonic, and resisitivity logs. Yes, I know this makes Schlumberger unhappy. Tough luck.

    The trick is to drill far and fast and to know where you are while drilling. They use "MWD" tools, (Measurement While Drilling) and directional surveys, (azimuth, depth, and angle) that is all.

    The hope is to stay within a known reservoir, or productive zone, for as long a distance as possible, set casing and (after multiple frac jobs) perforate a few thousand feet, then let that baby flow...(in layman's terms).