From what you wrote above, it sounds to me like the objective of the well is fairly shallow, perhaps even a coal bed methane play. (I am making an assumption here that when the well begins its 9000’ step out, it is maintaining a generally level depth below the surface.) In general, the deeper a well goes the higher the pressures. Higher pressures translate to a larger drainage area per well and therefore a rational for a bigger PA, spacing unit etc. The relatively small extent of the PA in one direction and a long extent in another indicates a low pressure regime and might be an explanation as to why a cigar shaped PA has been/will be approved. There could also be seismic evidence of faulting or other geologic barrier, which separates one tract from another.
As for determining the size and acreage included in the PA, the BLM will definitely consider seismic data, geologic data or even geochemical data if the operator presents it. This is good data to have, and is usually reliable, but at the same time it is not conclusive proof of what acreage is productive and what is not. Actual well data and pressures are necessary to establish a true drainage pattern. If actual well performance shows a larger area should be included in the PA, the BLM is bound to do so.
The BLM will not necessarily rubber stamp whatever PA is proposed by the operator, but the BLM will most likely not have independent seismic data to counter what the operator has proposed. They will simply have to decide if what the operator proposes is reasonable, given the data they have to review. If multiple other wells have been drilled into a similar reservoirs (by that I mean similar depths and objective formation) and shown over time to support the type of drainage pattern proposed by the operator, it will be difficult for the BLM to do anything different than what has previously been accurate without solid data to support a different decision.
While your acreage may not be included in the initial PA, the fact that the operator is drilling such a long step out means that they believe the productive formation extends over a pretty large geographical area. I wouldn’t be surprised given success in the first well that your acreage could be included in one or more subsequent Participating Areas.
Good luck to you,