GRAVITY OF OIL PRODUCED BY VARIOUS ZONES The average gravity of the oil produced from the first or upper zone is 20° Baum& This includes oil produced from the inter mediate edgewater sand in the central dome, which at this point has been grouped with the first zone.
The average gravity of oil produced from the second zone is about 25° Baum& It has been difficult, however, to obtain the average gravity of this zone, since wells which are producing from it are mainly in the central dome and are also producing from the first zone. The gravity of the oil in the second zone, as a whole, is apparently not uniform, the production from the upper portion being about 22° &tne and from the lower portion about 28° Baum& When the lower portion of this zone is produced with the upper portion and first oil zone, a mixture is obtained which averages 25° Baum& The gravity of the oil in the third zone, from the evidence obtained at the single well which has produced from this zone only, is about 30° Baum& It is, therefore, apparent that in this field, generally, the gravity of the oil increases with stratigraphic depth.
In general, also, it is apparent that wells on the flanks of the anticline produce heavier oil from the same zone than wells nearer the apex. Following is a tabulation showing the gravity of oil produced by zones: The results of the examination of this field show that on the whole the field is in very good condition, and as long as the in dividual oil zones are protected along lines used in the past, no unusual water troubles should develop.
In the three years which have elapsed since discovery of the field a total of 175 wells have been drilled or are now drilling. Of this number 112 wells are now producing, 30 wells are still drilling, 4 wells are idle and 29 wells abandoned. No dry holes have been drilled in the midst of proved territory and the wells which were abandoned were some of them located outside of the limits of the field and are now known to have been drilled too far down the flanks of the anticline. Others were abandoned and a few are
idle near the edge of the field and future development may indi cate that an insufficient depth was reached to secure oil. At such locations drilling may be resumed with fair prospects of success.
During the past year the majority of the wells were completed to produce from the first zone only. The total production of the field has been declining because the production from the second zone wells has been declining more rapidly than the production has been augmented by new wells drilled in the first zone. With a more extensive campaign in drilling into the second zone, how ever, there is no reason to believe that the production of the field may not exceed somewhat the maximum past production.
It may be mentioned again that the second oil zone is produc tive much further from the center of the field than is the first oil zone. In fact, along the line where the first zone ceases to be productive, the production from the second oil zone amounts to from 500 to 1000 bbl. per well per day. Edgewater sands in the second zone itself will probably be encountered near the edge of the proved territory, which will tend to complicate the drilling program for this portion of the field and will call for very careful work in outlining the position of such sands and arranging the drilling to produce the greatest amount of oil with adequate protection.
It should also be borne in mind that the lowest portion of the second oil zone and also the third oil zone can not be counted upon to furnish much production near the edge of the field on account of the prohibitive depth of these formations and also the possi bility of their carrying edgewater. The main production from these oil formations will undoubtedly be obtained in the central dome.
Following is a list of wells which contribute most of the water in this field, together with suggestions as to how such wells should be repaired.