It all comes back to Saudi as the "swing" producer-- meaning we can expect all data based upon KSA's "swings" in production to also swing back and forth as to URR.

As for me, I see induced swings in production in connection with the 2003 invasion of Iraq; and again in March 2004 and March 2006 to drop prices in the USA in time to influence our elections (is there someone who doesn't believe KSA cares about who controls Congress and the White House?).

I would suggest that a view of KSA production that identifies those periods when we can reliably believe that KSA was maximizing production (like in 1991, 2003, and early 2004 and 2006) based upon external events, could provide the most reliable set of data points. In every other case, the data could be because KSA was "swinging."

I would also suggest that the limited surges in 2003, 2004 and 2006 would likely be not a sustainable maximum, but the absolute maximum-- if KSA could have bumped production more in 1Q 2006 I believe that they would have, to give their BFF GWB more leverage in Congress. Just remember what happened to gas prices between Aug. 15 2006 and Nov. 1, 2006.

Regardless of what the actual number is, though, the USA should be acting, from a policy standpoint, as if the lowest number were the actual number, at least to generate some margin of safety.

And 150 may still be high since its not discounting more gradual changes in technology. The dogleg period is obviously the result of technical changes not some sudden large discovery and it obviously causes HL to produce a higher URR estimate.

Less obvious has been the continuous technical advancement over decades that has exactly the same effect. Inflating the URR reported by HL. This is because the URR determined by HL is actually two variables the rate of technical improvement in extraction capability and the real geologic depletion rate. Technical improvements are a two edged sword since they increase depletion rate but in general they make the final decline far steeper causing a large systematic overestimate of URR until technical advances no longer help.

The technology to extract oil has increased at a astounding rate topping out with the MRC wells in use today for primary and secondary recovery. We are still advancing to some extent in final recovery processes.

Assuming that this technical advance is effectively at its peak over the last few years means that we are no longer getting large production rate gains from technology.

The actual geologic peak was passed some time ago probably around 2000-2002 for global oil production. Increases in production rate since then have been because of aggressive technical extraction. Over the last few years we hit peak technology the peak production rate has nothing to do with the actual URR.

HL is still valid for predicting peak production but its URR estimates are probably invalid. The US happens to work primarily because technological advances in extraction within the US have been relentless. If we had peaked in technology earlier we would have seen that HL estimates for the US where to high.

These dogleg regions are one of the few ways we can get a good handle on the technical effect on extraction rate. And they point to a fairly large technical boost factor on the order of 50% higher extraction rates vs stagnant technology.
This means the real depletion rates are up to 50% faster than prediction by HL or more correctly the URR may be over estimated by up to 50%.

Now the flip side of the coin is that we can now probably maintain a high production rate to about 80-90% of URR but the decline rates are incredibly steep.

The technical peak then production a production profile close to a square wave on the post peak side.

So HL is still valid for determining peak since it is measuring both technical advances and real depletion rates.

Its simply a coincidence that the lower URR estimates also concide with time periods that prices where low or declining and thus technology was not being applied at a feverish pace. So these quite periods are a good time to calculate the real geologic URR.

This means HL used during times of stable low or falling prices is able to get the real URR since technical advances and aggressive drilling are much lower during these times.
KSA is tough because they actually shut in a lot of good production and this messes with the numbers.

If I'm right I find it funny that peak oil production is actually related to technology and has little to do with the geologic peak except its well after we have passed geologic peak. And its no surprise that the two are not offset by all that much since geologic declines are driving the technical advancements but the critical factor is they lead the technical decline in production rate. But its critical to understand whats happened the last few years is we have hit peak technology and can no longer mask the geologic decline.
Technical peak is effectively a ceiling or flat line and its boost effect goes almost directly to zero governed by the deployment rate. Most of the NCO's have rejected advanced methods in the last few years.

Look at the average production rate vs geologic depletion over time and you see we have been highly successful in keeping production rates high at the expense of faster depletion. Almost every method used to account for URR falsely includes this as a higher URR. No one has correctly subtracted the effect.

So in closing it seems we are actually 5 years or more post geologic peak and have lasted this long on a last ditch technical burst. If true then we will soon see some fairly steep global decline rates generally inline with natural depletion rates for fields that have been extracted using advanced technology these can be steep on the order of 15%.
This probably equates to the decline in overall production rate quickly approaching 5-10% globally over the next several years.

Peak Oil production rate has nothing to do with 50% URR except that it happens well after we have passed 50% URR.