Thank you for your quick response. Below, I have listed the descriptions for the mineral interests as they appear on the documents. I have included the royalty decimal when given, although I am not sure if this information is pertinent.
O.M. is my uncle’s mother.
1. The Quit Claim Deed 1969 (from my uncle’s sisters to my uncle):
Bounded and described as follows:
Being the SW ¼ of the NE ¼ of the SW ¼
2. A Division Order (Humble Oil) addressed to my uncle, dated 1969 with the notation that this interest formerly credited to and paid to O. M:
NE/4 SW/4 Wells-Goodall Unit .00260420 RI
3. A Division Order dated 1988 (Southstar Energy) my uncle as owner:
E ½ NE ¼ NW ¼ NE ¼ SW ¼ Wells Goodall .00260420
4. A Division Order from Southstar Energy listing O. M. as owner, dated 1988:
SE ¼ SW ¼ Weimer Ltd. .00781250
5. There are also 2 Division Orders from Conoco in 1997, both in my uncle’s name, but for different wells and decimals. However, both are missing any description beyond the section, township and range.
Wells Goodall .0039063
Austin Lee .0156250
Shortly after my uncle died the royalties began coming from Phillips66 rather than Conoco. The well names and decimals above match the interests currently receiving royalties from Phillips66.
6. The description on the Affidavit of Heirship filed for the trust in 2013:
The Northeast Quarter of the Southwest Quarter (NE/4 SW/4)
The Northwest Quarter of the Southwest Quarter” (NW/4 SW/4)
All descriptions are on one line, however the section, township and range may go into a second line. All descriptions refer to interests in the same section, township, and range.
The 1989 letter I mentioned from my uncle to Southstar Energy may refer to the Division Order issued to O.M.(#4 above.) In the letter he tells Southstar he inherited his mother’s interests in the McClain County field, but was unaware of its being in two parts. I do not know if this was ever resolved. The description on the Quit Claim Deed (#1) does not seem to match that on the Affidavit of Heirship (#6). The description on O.M.’s Southstar Division Order (#4) does not seem to match the interests listed in the Quitclaim Deed (#1) or the Affidavit of Heirship (#6). This makes me wonder if the confusion in 1988-1989 was resolved or if there may be other “lost” interests.
Based on this second set of information you gave, I don't believe there are any interests missing. Based on my experience, what probably happened is that many decades ago, an ancestor of your uncle(grandfather, great-grandfather?) owned the entire North Half of the SW/4, and either his will specifically left the NW/4 to one heir and the NE/4 to another heir, or those two heirs decided to "partition" the North Half into two equal pieces. This is done by a Deed signed by both heirs, one of them giving the other one 100% of the rights to the NW/4 of the SW/4, and the other one giving that one 100% of the rights to the NE/4 of the SW/4. Then whichever heir who got the NE/4 of the SW/4 either sold off smaller quarters of it while still alive, or bequeathed pieces to children and over time the SW/4 of the NE/4 of the SW/4 came into possession by your uncle's sisters and they agreed to sell their share to your uncle.
Your uncle could have been the sole heir to the NW/4 of the SW/4 and already owned it when he bought his sisters' interests.
As for the division orders, it's important to know that the legal description on a division order is not for the land owned by the owner named in it and being asked to sign it. It is a description of either the legally-pooled unit from which the named well is considered producing by the state agency in charge of oil and gas production oversight, or it is the legal location of the well drill-site acreage without describing the entire unit.
When your uncle bought your sisters' interests in their lands also included in the Wells Goodall and Austin Lee wells, his decimal increased. In 2005 Phillips 66 merged into Conoco Oil Company and the name was changed to ConocoPhillips. That's probably the company name you are seeing on division orders and checks.
I hope I've answered your question. If not, please don't hesitate to write me another follow-up with whatever questions I've missed, and I'll provide the additional information if I can.