A few things I'm wondering about. Are the oil tanks involved in this case big enough for an adult to fit through the opening? Yes. They are about 20-30 ft high and can hold 20,000-30,000 gallons. The manway usually has a diameter of 24-36" so people can go in to repair or inspect the tanks. Did he intend to put SW in one as well? Was she too big, being an adult, for him to get her into the tank? Not too big, but problem would be climbing 20-30 ft. with an adult body. Where was the oil destined for? This was crude that was considered a contaminant in a gas well. In a gas well, the amount of crude would be lower than in an oil well. It would probably take a year before that tank would be empty, but it was close to full. Are the tanks ever drained otherwise? Yes, when the crude is sold or when the tank needs to be repaired like if a weld needs to be repaired. When oil is removed from the tanks, is it for processing? Yes Sale? Yes Transfer? Yes. May go to a refinery to separate out the various chemicals. Also is mixed with sand to produce asphalt. Would decomposition byproducts become noticable? Would depend on when found. With a high level of decomposition, the materials in the body would be the same as chemical composition of oil. Even calcium from bones would not be noticeable since it is a naturally occurring element in some rock like limestone. Would the oil restrict or aid decomposition? Would depend on the chemicals in the crude. It will vary from location to location. Are they going to find internet searches on these types of questions? I doubt it, but if you have worked around crude tanks, you would know this and he worked for a gas company and tanks. He would know the answer to all of these questions from experience. The crude is thick and sticky. After 4 days that would likely have sank some into the crude and probably couldn't even been viewed. Were the oil tanks something he thought of before or after the murders?
In spite of things that have rubbed others the wrong way (I get it), I feel like N bit down like a pit bull and wouldn't let go when she sensed something was wrong. Had she not been so persistent and involved LE so quickly, it's possible that CW would have had more staging time, making this case that much harder for authorities to solve and prosecute.
Edited for spelling.