Interesting research friend @tomlee, I am passionate about reading your articles on drilling fluids, because sometimes I feel lonely when I publish this kind of topics, but since I discovered your articles I have already found a source to rely on.

I think it would have been good to compare the cost per bag of foreign bentonite, which is what you export, and compare it with the additives added to the local clay (sodium carbonate and barite). And in this way fully demonstrate the feasibility of the use in terms of cost optimization.

Regarding that the calcium carbonate decreases the acidity of the drilling mud and increases its PH, it is very favorable for the corrosion of the equipment, the other thing that can be studied and evaluated is also the impact that the ph and the acidity of the drilling mud have to run electrical records to evaluate the resistivity of the formation.

Referring to the density, I believe that the first thing that must be evaluated is what reservoir pressure is handled in the oil fields of greater pressures in nigeria, since if initially without barite the local clay handles 8.2 Lbs/gal of density, for example can be calculated the hydrostatic pressure that exerts that fluid for example to 5000 feet of depth with the following equation: Ph= 0.052 x 5000 feet x 8.2 lbs/gal, which implies that the hydrostatic pressure that fluid will exert with that density and at that depth is Ph= 2132 Lbs /square inch (PSI), then if for example if the reservoir pressure at that depth is 1600 psi, there would be no problem with a dummy and a possible blowout, Since there would even be approximately 500 psi of overbalance in favor of the hydrostatic pressure of the drilling fluid, of course this means that if we go deeper into the well we will find ourselves with increasing reservoir pressures, and if we need to increase the density at any necessary point there we need to add barite as a densifier.

Now for the other case you mentioned of fracturing the formation and that a loss of circulation can occur, this is really dangerous, because even this is another cause for which a blowout occurs, since the loss of drilling fluid, decreases the column of fluid and therefore decreases the hydrostatic pressure, and may be below the pressure of the reservoir. To control this it is necessary that the hydrostatic pressure never exceeds the formation's fracture pressure, this fracture pressure is just below the last casing shoe, this fracture pressure value must always be noted on the Company man's blackboard at the location where the well is being drilled.

As you can see friend @tomlee my comment is somewhat extensive, but it is that you inspire me to write since the topic that you mention excites me, since it touches my profession, greetings friend and I hope to be reading very soon with more of your articles related to investigations to improve the local clay drilling fluid of your country Nigeria, God bless you and have many successes.