Abstract

We analyzed organic and inorganic volatiles from Cantium’s Gulf of Mexico OCS–G 04903 A008 ST1 well cuttings, Main Pass 41 Field; the well was drilled with oil-based mud (OBM). This 2018 sidetrack produces from deep sand. Unpreserved wet cuttings from the top 600 ft of the sidetrack and the lower 2600 ft of the sidetrack were analyzed utilizing rock volatiles stratigraphy (RVS). Unpreserved cuttings were high graded to individual sand grains to remove residual mud. The producing interval was identified using RVS parameters including the presence of non-water-soluble aromatics, biological products like methylethylketone (oil soluble byproduct from consumption of n–butane), oil soluble sulfides, and compositional parameters like gas-oil ratio (GOR). At least 9 different parameters correctly identified the pay sand, agreeing with wireline analysis. RVS data also indicated separate chemical compartments/seals correlating to seismic, residual oil saturations, evaluated biological activity, and identified on potential for up dip/shallower pays and oil migration, reducing risk.

RVS, developed by Advanced Hydrocarbon Stratigraphy and available through Baker Hughes as Volatiles Analysis Service, analyzes entrained organic and inorganic volatile chemistries of geological materials; i.e., cuttings and/or core. RVS custom built/developed cryotrap–mass spectrometry systems gently extracts, identifies, and quantifies volatiles. Samples are fresh cuttings/core hermetically sealed at the well, or unsealed/legacy materials up to several decades old.

The Gulf of Mexico can be very challenging for geochemistry of cuttings. The young and cold unconsolidated sands lack sufficient diagenesis to form native fluid inclusions. Polycrystalline diamond compact (PDC) bits, OBM, and unpreserved samples further complicate matters. RVS analysis succeeds in the Gulf of Mexico as RVS analyzes fluids/gases entrained in tight pore spaces/cracks of individual sand grains, is highly sensitive, and is insensitive to OBM. Successful analysis of legacy unpreserved cuttings offers new opportunities for well postmortems, petroleum system analysis, and mature asset exploration. RVS offers new inexpensive exploration insights from legacy cuttings and cores, such as the Texas Bureau of Economic Geology maintains, from 5000+ wells in a 100 mile radius of New Orleans.