SU819320A1 - Method of measuring formation pressure - Google Patents

Description

(54) METHOD FOR DETERMINING PLASTIC PRESSURE

I

The invention relates to the oil and gas industry, in particular to the operational prediction of reservoir pressures during exploratory drilling in the conditions of AHF conditions.

There is a known method for determining the formation pressure gradient, in which in the immediate vicinity of the bottomhole a well is pumped in several stationary modes of operation of a mud pump, the mud flow rate, gas concentration and pressure in well 1 are measured.

This method has the disadvantage that in the case of simultaneous gas injection of several previously opened formations, the accuracy of determining reservoir pressure sharply decreases, or the determination of reservoir pressure becomes impossible.

There is also a known method of testing several horizons in one descent of a tool 2.

This method also has a number of disadvantages. It is impossible to measure reservoir pressures in all hectares of the developing strata in the following cases:

1. If there are cavities in the walls of the open hole (due to the impossibility of packing).

2.B open trunk with a different (stepped) diameter.

3. In cases when, when testing the first formations, the packer element is damaged.

4. In ultra-deep wells with abnormally high temperatures (the material of the rubber sealing element loses

elasticity).

In addition, the method of testing several objects in one flight requires the use of expensive, complex test tools.

The aim of the invention is to simplify the method.

Claims (2)

This goal is achieved by measuring pressure and flow at successive levels at different levels and simultaneously taking a sample at each level and determining the gas concentration in it. At the depth of the lower end of the drill pipe set depth gauge. The sequence of operations in the implementation of the proposed method is as follows. Drill pipe down to the bottom (depth L) with a depth gauge at a depth of the lower end and a device for landing a depth sampler for sampling drilling mud from the annulus at a height h from the lower end of the pipes. Flushing is performed at several stationary modes of operation of the mud pumps with flow rates q, q q. Depth samples of the drilling fluid are taken on each of the modes and the gas concentration in them is measured; K, Ki, Kj. The depth gauge measures the pressure, Pj. Then the drill pipes are raised and the described operations are repeated at a depth Lj. Then again, the rise and new measurements. The measurement data is tabulated and, after graph-analytical processing, the predicted value of reservoir pressure at the required depth is obtained. Example. Initial data. The depth of the well is 6000 m. In the interval of 5,500–6,000 m of the open borehole, gas passages are noted. It is required to determine the predicted pressure at a depth of 6200 m. We perform flushing of the well with flow rates q 0.025, q 0.040, q 0.050 m3 / s at depths of 6000, 5940, 5880, 5820, 5760, 5700, 5640 m. The device for landing the depth sampler is set at 60 m from the lower end of the drill pipe. At each of the modes of operation of the drilling pumps and at all depths, depth samples were taken and the concentration of gas in the drilling fluid was measured. The segments cut off on the y-axis correspond to the square of the reservoir pressure. It follows from this that the reservoir pressures in the middle of these intervals are equal. Pa: Pn (5970) U9790-10 98.95-106 р „. {5850) U9360-10 96.75-10 Rpl (5670) V8815102. 93.89-106 Dividing the obtained reservoir pressures to the depths of the middle of the corresponding interval, we obtain reservoir pressure gradients. We build a graph of the change in the gradient of the reservoir pressure and extrapolate it to a predetermined depth of 6200 m. We obtain the predicted gradient of the reservoir pressure equal to 16.71-106 Pa. The predicted reservoir pressure at a depth of 6200 m is equal to: FIR 16.71-W-6,200 103.6-106 Pa. The described method allows predicting reservoir pressure 1.5-2.0 times faster than previously known ones, which, in turn, reduces the time of well placement with a significant increase in forecast accuracy. The method of determining the reservoir pressure, which consists in flushing the well in several stationary modes of operation of the mud pumps, measuring the flow rate of the drilling fluid, the gas concentration in it and the pressure in the well, in order to simplify the method pressure and flow are measured sequentially at different levels and at the same time a sample is taken at each level and the concentration of gas in it is determined. Sources of information taken into account in the examination 1. Express-information "Geologists, drilling and development of gas fields, No. 14, VNIIEGAZprome. M., 1978, p. 14-16. 2. Oil business number 5, 1978, p. 24-26.