by rockdoc123 » Sat 17 Sep 2016, 14:47:20
$this->bbcode_second_pass_quote('', 'T')hus the key question, when do production declines for Ghawar set in? What rate do they set in at, 3%, 6%, 9% per year? If they are over 50% depleted now and are ultimately going to reach 70-73% in 20 to 30 more years of production how soon will we know they are on the declining output slope?
A difficult question to answer given we don't really know how hard the remaining wells are being produced. Theoretically if you have 200 wells producing fullout and shutin 100 as the waterflood front passes by you would end up with 50% less production. But if the wells have been produced at very low drawdown and have lots of room to have production increased then that isn't the case. You could shutin one well and increase production in one or more wells to make up for it.
Interestingly enough I did come across something I had saved from a post I made here back in 2006 (I think). In that post I quoted some work done by WoodMac
$this->bbcode_second_pass_quote('', 'A')s of January 2006, aproximately 43% of Saudi's initial commercial oil reserves had been produced and at the estimated 2006 production rate, around 2% of remaining oil reserves (WoodMac estimates 145 MMB 2P) are being produced annually. Within these figures we include Saudi's 50% share of all oil and gas fields within the Partitioned Zone.
Back then I used Woodmacs daily production numbers and remaining 2P to arrive at the following field depletion ratesOnshore portioned zone = 6.8%
In that same post I quoted some comments from I'm not sure where, which is in line with what I mentioned about new wells:
$this->bbcode_second_pass_quote('', 'B')ut Saudi Aramco has taken a number of measures to offset a decline in output from the country's aging oil fields, the spokesman added. "A variety of remedial activities are always being taken in oil fields influencing their effective decline rates," the spokesman said. "The drilling of additional development wells in the producing fields is Saudi Aramco's standard practice to offset normal declines of older wells."
This is particularly important when oil fields are progressively depleted under a well thought out strategy of maximizing the sweep and displacement efficiencies, leading to high ultimate oil recovery, the spokesman said.