RU2016134036A - INDICES OF STRUCTURAL DIFFERENCE OF UPPER ZONES OF FILLING THE ORDOVICIAN Limestone AND METHOD FOR DETERMINING THEM - Google Patents

Claims (26)

1. The method of determining the structural differences indices of the upper filling zones of the Ordovician limestone, according to which: first, three types of fill zone structures are determined, namely, a continuous filling structure, a discontinuous filling structure, and a free-filling structure; then, the difference indices are determined in accordance with three types of structures of the filling zone, including: q value of water breakthrough to the well, Q flow rate of underground water and permeability coefficient K of the Ordovician limestone section; then, respectively, determine the threshold values for each index in accordance with various waterproof properties corresponding to the specified three structures; moreover, the indices are obtained through the following steps: a) first, extensive sampling is performed at the places where the filling zones exit to the formation surface to study the state of filling of cracks with clay in the filling zone, and the filling zones are distinguished by the degree of filling of cracks: a structure with continuous filling, a structure with intermittent filling, and a structure free from filling in; classifying the types of filling zones corresponding to the three structures of the filling zone, respectively, as a water-resistant filling zone, a weak water-resistant filling zone and a water-saturated filling zone; b) for the filling zone at a depth of more than 300 m, three indices of the structures of the filling zone are determined in accordance with the test results of injection / flow rate, namely: the q value of water breakthrough to the well, the flow rate Q of underground water and the K coefficient of permeability of the Ordovik limestone section by the following steps: b1) get the q value of the breakthrough of water to the well: comprehensively determine the depth of development completion in the filling zone in accordance with the core removal coefficient, displacement fluid flow rate and the degree of development of clay rock in the well; the depth of completion in the filling zone is defined as the depth of completion of the development of clay rock, where the core removal coefficient is less than 50%; Thus, a site for testing by water injection is defined as a section starting from the starting point of the Ordovician limestone to this depth, and the q value of this section is calculated by the formula (1):

where Q is the flow rate of the well, m ³ / s; M is the thickness of the water injection site, m; s _w - lowering the water level in the well, m; R is the radius of influence of the well, m; r _w - well radius for water injection, m; b2) receive the value of the flow rate Q of groundwater: perform a test to determine the flow rate of water for an underground well and record the value of the flow rate of water in the area every 2 minutes; for tests to determine the flow rate of groundwater that have not previously been performed with such a high recording rate, they analyze the recorded values of the water flow rate by approximation, as an example explaining the approximating formula for determining the flow rate of water for one well, the values of the flow rate at different water depths are obtained, starting from the starting point of the Ordovician limestone, according to the approximating formula (2):

where, x - depth in the Ordovician limestone, m; Q - the amount of water breakthrough at various depths in the Ordovician limestone, m ³ / s; b3) obtain the coefficient K of permeability: for an underground well, a water flow test is performed, and with the valve closed at the site during the water flow, the static water pressure P ₁ and the instantaneous water pressure P ₂ are recorded, respectively, to represent the water pressure in the area when tested on water consumption; calculate the actual value S of the decrease in water level in the process of water flow, and calculate the coefficient K of permeability in the area according to formulas (3) and (4):

where K is the permeability coefficient, cm / s; the values of other parameters are the same as in formula (1); c) determine threshold values for the q value of water breakthrough to the well, the flow rate Q of underground water and the permeability coefficient K by the following steps: c1) determine the threshold value q of the breakthrough of water to the well: since the structure with continuous filling is water-resistant, and when tested by water injection, the water injection section exhibits water-resistant properties at q <0.001 l / s · m, the section with the value q <0.001 l / s · M is defined as a water-resistant filling zone; since the intermittent filling structure has low water permeability and when tested by water injection, the water injection section exhibits the property of low water permeability at 0.001 <q <0.01 l / s · m, the section with a value of 0.001 <q <0.01 l / s · m as a filling zone with low permeability; since the structure, free from filling, is water saturated and when tested by water injection, the water injection section exhibits water saturation at q> 0.01 l / s · m, a section with a value of q> 0.01 l / s · m is defined as a water-saturated filling zone; c2) determine the threshold value for the flow rate Q of groundwater: the water content in the structure of the filling zone is the same as in step c1); the threshold value for Q is obtained as the product of the threshold value for the quantity q determined in step c1) and the average decrease in the water level at a depth of more than 300 m; based on the position of the coal seams of the lower group at a depth of more than 300 m, four levels of water pressure of the Ordovician limestone are determined, that is, 3 MPa, 4 MPa, 5 MPa and 6 MPa, respectively; in addition, a decrease in water level during the injection / flow test is assumed to be the maximum level of decrease, i.e., 300 m, 400 m, 500 m and 600 m, respectively; thus, determining a threshold value for the amount of water breakthrough to the well; c3) determine the threshold value for the coefficient K of permeability: the water content in the structure of the filling zones is the same as in step c1); since the test site exhibits a water-resistant property when tested by injection, when the permeability coefficient K is K <10 ^-5 cm / s, a site with a value of K <10 ^-5 cm / s is defined as a water-tight filling zone; since the test site exhibits the property of low water permeability when tested by injection, when the permeability coefficient K is 10 ^-5 <K <10 ^-4 cm / s, a site with a value of 10 ^-5 <K <10 ^-4 cm / s is defined as a weak filling zone water permeability; since the test site exhibits the property of water saturation when tested by injection, when the permeability coefficient K is K> 10 ^-4 cm / s, a site with a value of K> 10 ^-4 cm / s is defined as a water-saturated filling zone. 2. A method for determining the structure, comprising the following steps: determine the types of filling zones and the thickness of each of the filling zones in full accordance with the estimated indices and threshold values determined in accordance with the method of claim 1, wherein the water-resistant filling zone can be directly used as a water-resistant formation; the poor permeability filling zone can be modified by cementation and then used; the water-saturated filling zone cannot be used as a water-resistant formation, since it has the same water permeability as the underlying Ordovician limestone; plot the isolines of the thickness of the water-resistant filling zone, the isolines of the water breakthrough coefficient without taking into account the water-resistant filling zone, and the isolines of the water breakthrough coefficient taking into account the water-resistant filling zone, respectively; compare and analyze two maps with contours, and determine the safe area for coal mining in the lower group.