From sedimentological and oil-geological view point, the writer investigated the sandstones of the Shiiya and the Nishiyama stages in the northern part of Higashikubiki, Niigata Pref., Japan. The sandstones in this area are composed of material supplied from the topographical high place by mass flows such as turbidity currents and thick sandstone developes in WNW-ESE and -SE directions decreasing thickness and turbulence to the marginal area. And in the papers of "Part II", the writer will discuss various properties as petroleum reservoir taking into these sedimentological considerations.
Based on the Mathematical point of view, the problems concerning the optimum well spacing are investigated. Therefrom, two methods for determinating the most profitable number of wells to be drilled are introduced as follows, (1) The solution by means of the linear programming (L. P.) and (2) The mathematical analystic solution. For the L. P. calculation, the linear constraints on the well pressure, oil originally in place and processing capacities are fixed, and the objective=profit function are simultaneously formulated. Then using the simplex tableau, the optimal solutions to obtain the most profitable production scheduling are derived for the given number of wells and limited production life of the oil field. By plotting the present value profits versus the various number of wells to be solved on the graph paper, the optimum well spacing for any oil field is quantitatively estimated. On the other hand, assuming the petroleum production declines exponentially, the present value profit is represented as the contineous function of the number of wells. Then the primary differential calculation. is applied to determine the most profitable number of wells. In spite of the lack of considerations concerning the complicated reservoir conditions, it is thought that this method has the advantage to be straightfoward and practical in its application.
In order to clarify the jet action of drilling bit, pressures of submerged jet of water or bentonite mud at a bottom of confined cylider were measured. Results obtained were: (1) When cylinder diameter is 11 times greater than dozzle diameter, the relationship between velocity at nozzle and velocity at the center of a bottom plate is same as those obtained by others. When cylinder diameter is smaller than this value, the relationship is affected by both cylinder diameter and fluid viscosity. (2) For understanding the jet action of bit nozzle the momentum of jet divided by fluid density is the most reliable. When this momentum is same at different nozzle sizes, Pressure distribution on bottom plate have same value and, therefore, jet actions are considered to be same.