My thinking was that the northern parts of the field is today nearly depleted much more so then saudis would like to admit and probably require a lot of capacity today to separate oil from water. Perhaps today vertical wells has been modified into horizontals creaming the top of whats left with high water saturation?
I would love to hear an opinion about my guess from those of you with real experience even if its just an educated guess.
I don't know very much about Ghawar, not as much as Burgan in Kuwait. What I have read about Ghawar suggests to me for many years the oil water contact was moving up structure fairly uniformly at a predictable sort of rate. Then, as is mostly always the case in water driven fields, "bottom" water begins to break thru in wells high on the structure forming unpredictable, irregular drainage patters around wells. The term for that is fractal drainage. It then becomes hard to determine where to drill wells along the structure to avoid initial water production because there is no longer a uniform, known oil water contact. They have also been re-injecting water from structurally low positions in the field for a long time also, I understand.
I am not an engineer but common sense then suggests to me the thing to do is make a plan to move lots of water from the apex of the structure, which they do by drilling laterals at the very top. Horizontal laterals are sort of like a long, below ground pipeline with lots of vertical wells drilled along the pipeline (perforation stages). Horizontal laterals increase reservoir "contact" and greatly increase conductivity from the reservoir to the well bore. Given the nature of reservoir in Ghawar (unlike dense shale it has good permeability and porosity) it suggests to me that the Saudis drill these laterals and then put those wells on ESP, or gas lift, whereby they can move 2000 barrels of total fluid per day or more. If those wells have a OWR of 40%, they are good wells. They can handle that amount of water and build massive systems to separate and treat the water before reinjecting at low structural positions again that, in theory, pushes oil up structure. It becomes a sort of "rinsing" process. The structure is full of water but you can keep "cycling" that water and rinsing interstitial oil out of the rock for a long, long time. OWR rates can ultimately got down to 10% or less and still be economical.
Make no mistake, water production IS the beginning of the end but when the structure gets to that state it is a long way from dying overnight. The rinsing can go on for many years and lots of additional oil can be recovered. Ironically the Yates Field in Pecos County I just wrote about is in a similar state and is being produced much the same way. Some suggest Yates will produce another 25% of its OOIP by moving lots of water over the next 35 years.
Thanks for long and extensive answer Mike, i believe this is exactly what has been happening for many years now massive drilling and then massive capacity to "rinse" and repeat the procedure.
Probably takes a lot of capital and effort today to maintain production somewhat, remember i saw somewhere they were putting several hundreds of new wells in each year.
A while ago i wrote this regarding a discussion about Ghawar
My thinking was that the northern parts of the field is today nearly depleted much more so then saudis would like to admit and probably require a lot of capacity today to separate oil from water. Perhaps today vertical wells has been modified into horizontals creaming the top of whats left with high water saturation?
I would love to hear an opinion about my guess from those of you with real experience even if its just an educated guess.
I don't know very much about Ghawar, not as much as Burgan in Kuwait. What I have read about Ghawar suggests to me for many years the oil water contact was moving up structure fairly uniformly at a predictable sort of rate. Then, as is mostly always the case in water driven fields, "bottom" water begins to break thru in wells high on the structure forming unpredictable, irregular drainage patters around wells. The term for that is fractal drainage. It then becomes hard to determine where to drill wells along the structure to avoid initial water production because there is no longer a uniform, known oil water contact. They have also been re-injecting water from structurally low positions in the field for a long time also, I understand.
I am not an engineer but common sense then suggests to me the thing to do is make a plan to move lots of water from the apex of the structure, which they do by drilling laterals at the very top. Horizontal laterals are sort of like a long, below ground pipeline with lots of vertical wells drilled along the pipeline (perforation stages). Horizontal laterals increase reservoir "contact" and greatly increase conductivity from the reservoir to the well bore. Given the nature of reservoir in Ghawar (unlike dense shale it has good permeability and porosity) it suggests to me that the Saudis drill these laterals and then put those wells on ESP, or gas lift, whereby they can move 2000 barrels of total fluid per day or more. If those wells have a OWR of 40%, they are good wells. They can handle that amount of water and build massive systems to separate and treat the water before reinjecting at low structural positions again that, in theory, pushes oil up structure. It becomes a sort of "rinsing" process. The structure is full of water but you can keep "cycling" that water and rinsing interstitial oil out of the rock for a long, long time. OWR rates can ultimately got down to 10% or less and still be economical.
Make no mistake, water production IS the beginning of the end but when the structure gets to that state it is a long way from dying overnight. The rinsing can go on for many years and lots of additional oil can be recovered. Ironically the Yates Field in Pecos County I just wrote about is in a similar state and is being produced much the same way. Some suggest Yates will produce another 25% of its OOIP by moving lots of water over the next 35 years.
Thanks for long and extensive answer Mike, i believe this is exactly what has been happening for many years now massive drilling and then massive capacity to "rinse" and repeat the procedure.
Probably takes a lot of capital and effort today to maintain production somewhat, remember i saw somewhere they were putting several hundreds of new wells in each year.