Interesting Article On Waterflooding & The Ain Dar Gas Cap

[hatrack]

By using oil well locations and approximate ages identified using Google Earth, geo-referenced well spacing maps, and several SPE publications, a more complete picture of the status of the 'Ain Dar operational area of the Ghawar oil field is obtained. Recent wells have been drilled in the very top of the Arab-D reservoir and in areas where an uneven water flood has left oil behind. The location of gas caps, one each in north and south 'Ain Dar, overlap with the remaining dry areas present in 2004.

Getting Wet
The northern part of the 'Ain Dar area is the most mature part of the Ghawar oil field, and the water flood used to maintain production levels has been monitored for many years. A paper published in 2005, SPE 93439: Water Management in North 'Ain Dar, Saudi Arabia , discusses several strategies for reducing water production from the field. Figure 5 from this paper shows the flood front advance through the mid 1980s. As shown in the image below right, there has been quite a number of wells drilled to the south of the study area in the past few years, including some wells being drilled in May 2006. Given that 20 years have passed, how much oil is left to be had there?



Stuart Staniford of The Oil Drum has used this information along with data from other publications in an investigation of how much oil is left. One resource he used was a paper by Hussain et al Optimizing Maximum-Reservoir-Contact wells: Application to Saudi Arabian Reservoirs presented to the 2005 International Petroleum Technology Conference (IPTC 10395). This work focused on the optimization of two MRC (maximum reservoir contact) wells in south 'Ain Dar (identified as ANDR-"XYZ") and one in Shedgum (SDGM-"PQR"), but it also briefly described another MRC well in 'Ain Dar (ANDR-"ABC"). Diagrams of these wells showed their locations relative to nearby wells along with oil column thickness in the vicinity. Staniford ascertained the location of ANDR-"XYZ" as being in south 'Ain Dar.

Using the well placements determined using Google Earth, I have identifed the precise locations of the other two wells, with ANDR-"ABC" being located in north 'Ain Dar midway between GOSP-2 (Gas-Oil Separation Plant #1) and GOSP-1. This was the first MRC well placed in north Ghawar as also described in the Water Management paper cited above. According to Saudi Aramco, the motivation for placing this well was to "provide an additional oil producer tied into GOSP-2 to maintain plateau, to reduce the average water cut of the field, and to increase oil recovery". Despite the obligatory alphabetical coding for secrecy, the real identities of the two 'Ain Dar wells are revealed as ANDR-524 (north) and ANDR-550 (south). As noted previously, this gives a number for the wells developed in the time span between them as approximately 26. This simple correlation is rather useful, but even more useful is my chance recognition of the profile of northern 'Ain Dar in a paper presented at the 25th Annual ESRI International User Conference (2005) entitled "Well Placement Optimization Using GIS", hereafter referred to as the "ESRI" paper.

EDIT

http://satelliteoerthedesert.blogspot.com/2008/01/water-under-gas-cap-in-ain-dar.html