Does anyone know any public sources for GIS leaseholding data for large players in the Oil & Gas industry. I would like to get my hands on leasehold polygons of large producers like Chevron, Exxon, etc. To my knowledge this is all public data, and in no way private, correct?
There are couple of ways of getting hold of this data. Firstly directly via National Data Repositories which are data bank's that commonly hold information on natural resources data. Including licence blocks, wells etc
The data is publically available, as it is a way of publicising natural resource, but can be spread across several regulators and agencies (in USA Federal Ocean Management vs New Mexico State and Texas Land Office) within a country as well as individual governments (e.g. Scotland vs. England). You will have to look into each country to get hold of the information and understand juristiction and how the data is distributed. For example:
This will take a while unless you know which countries you can focus on. I have found that licence information is readily available in GIS format with attributes within Western Europe and USA normally through a primary website or through a bit of digging through different regulators. Outside of Europe and the USA it quickly becomes much harder to reserach and get hold of spatial data without resorting to georeferencing and digitising your data. Try getting hold of Iraqi Kurdistan, Ghana, Nigeria, Egypt, Mexico licence blocks from their government sites.
Based on my somewhat limited experience, no, this is not public data. Or rather parts of it are and at certain levels, but not in aggregate and as directly attributed to the large companies in the way you ask.
Companies are in no way obligated to publish any data at all regarding their leases. They do submit data to various regulatory agencies and governments, which may be public, but this relates more to wells than leases. Leases on public lands may be trackable through public record at a centralized source or two (say BLM or state as spk578 mentions), but for private lands you'd probably have to go to the county level. There, oil and gas leases (OGLs) or memorandums thereof are filed. They don't always contain all the details about a lease either - some or all terms can be withheld from public record. But at that point you're searching document types, not GIS data.
You also have to look at the industry structure. While I'm sure the big companies do directly hold their own leases, there are also a lot of production companies that sit between them and leaseholders as well. Individual brokers acquire leases for various companies which may be production companies or just holding/investment companies that in turn sell those to producers. They also joint lease or sell rights around (competitors can own percentage rights of the same lands). From your question maybe you're only interested in lease polygons that are directly held by the big guys, but I've seen where that's done through subsidiaries under completely different names.
As spk578 mentions, there are companies out there that gather and sell this type of data. Another one is P2 Energy Solutions, and their lease info page suggests they do a lot of legwork at individual county offices to track and keep current leasing information.
I'm not an experienced oil and gas guy or landman; I came in from the GIS/mapping side. I've been doing mapping work for a broker about a year and a half now, and this is all based on that experience. I know I have been supplied proprietary information about leaseholds in an area before in order to produce maps, but don't know much about the source (and probably couldn't share it under NDA if I did). I know the broker has title examiners who track down mineral rights on lands, and I know they reference/research (and I mostly work with) county record documents. But I don't know what other sources they use, possibly including a paid information service as mentioned above, because I'm not a landman or title examiner. I'm just the mapping guy who produces the individual lease polygons you're talking about and sends them up the chain, and in some/most cases that's all done internally to the company as private, proprietary data.
One work around for HBP acreage is buying some standard well DBs from someone like www.petroswell.com , www.whitestar.com, or mapsearch.com, and then dissolving by operator and/or lease, you can add generic color coded buffers based on acres in lease(idk about whitestar and mapsearch, but petroswell has an acreage column), and it will give you a good overview of a county or area, and you can see basically who is doing what and where.