RU2250365C2 - Method for extraction of gas-hydrate deposit - Google Patents

Abstract

FIELD: gas industry.

SUBSTANCE: method includes drilling sub wells from bed with terminal high-pressure waters, laying lower relatively to gas-hydrate deposit, with horizontal branch under sole of gas-hydrate deposit for flowing thermal high-pressure bed water from lower level to higher level. Then gas extraction is performed while supporting pressure in extracted deposit and drilling gas-draining wells with vertical shaft to surface. First, at the beginning of gas-hydrate deposit sub well is drilled to bed with thermal high-pressure waters for feeding bed water into gas-hydrate deposit. Branch below soil of gas-hydrate deposit is made by horizontal wells. Then drilling is performed in upper portion of gas-hydrate deposit, of horizontal gas-draining wells with vertical shafts to surface. Thermal bed water debit, necessary to process 1 m³ of rock, is calculated from mathematical expression.

EFFECT: higher gas yield.

2 cl, 1 ex, 1 dwg

Description

The invention relates to the field of the gas industry, in particular to methods for intensifying hydrocarbon production, and can be used in the development of hard-to-recover gas deposits, including gas hydrate.

A known method of developing a gas hydrate deposit, including creating a fracture by hydraulic fracturing, pumping a heat carrier into a crack with a temperature higher than the temperature of the reservoir and delivering decomposition products of gas hydrates and a cooled coolant to the surface, moreover, a hydraulic fracture is created at the bottom of a gas hydrate reservoir and water is pumped from the surface or from an underlying aquifer horizon (see USSR author's certificate No. 1574796, 5MPK E 21 B 43/16, publ. 30.06.90, bull. No. 24).

The disadvantage of the described method is the lack of gas recovery efficiency due to the low coverage of the formation by vertical production wells.

Closest to the proposed method in terms of technical nature and the achieved result is a method of developing a gas hydrate deposit, including drilling bypass and production wells in the rock, followed by production through gas bypass wells while maintaining pressure in the developed reservoir by transferring thermal high-pressure formation water from the underlying horizon to the overlying at the same time, a perpendicular well is drilled to a reservoir with thermal high-pressure waters lying relative to the gas hydrate deposits, operate the horizontal branch gas hydrate deposits under the sole for supply of formation water and the drilling of a well with flue vertical outlet to the surface (see. SU №1574796, 30.06.1990, 5 sec.).

The disadvantage of the described method is the lack of gas recovery in the development of hard to recover gas deposits. This is due to the fact that the location of the bypass wells along the periphery of the deposit slows down the process of heat transfer, heat transfer, phase transition, displacement of gas in the sorted state, in solid solution and in low permeability reservoirs due to the low pressure coverage of the developed reservoir and the limited area contact and heat transfer, and consequently, prolonged and inefficient extraction of gas hydrates, characterized by insufficient permeability, displacement and decomposition iem.

The invention is aimed at ensuring the intensification of the development of gas hydrate deposits, namely, increasing the gas recovery of the reservoirs on the scale of the whole reservoir by maximizing its coverage over the area.

When implementing the invention, the task is achieved: increasing the efficiency of developing hard-to-recover gas sources due to thermal effects, expanding the pore and crack volume, decomposition, gas hydrate phase transformations, gas displacement and dissolution under the influence of pressure drop.

As a result of solving these problems, a technical result is achieved - expanding the scope of technology for the extraction of gas from hydrate accumulations.

The problem is achieved by the fact that by the method of developing a gas hydrate reservoir, including drilling bypass wells to the formation with thermal high-pressure water, lying relative to the gas hydrate reservoir, with a horizontal branch below the bottom of the gas hydrate reservoir to bypass the thermal high-pressure reservoir water from the underlying and subsequent horizon gas production into the overlying horizon maintaining pressure in the developed reservoir and drilling gas vents with vertical outlet to the surface, first in the central part of the gas hydrate deposit, a bypass well is drilled to the reservoir with thermal high-pressure water to supply formation water to the gas hydrate reservoir, branches under the sole of the gas hydrate reservoir are drilled by horizontal wells, then the horizontal gas discharge wells are drilled in the upper part of the gas hydrate reservoir at the vertical this flow rate of thermal formation water required for processing 1 m ^{3 of} rock, take:

where q is the rate of thermal formation water;

With _n - heat capacity of the rock, kcal / m ^3,0 C;

С _T - heat capacity of thermal formation water, kcal / m ^3.0 С;

Δ T = T ₀ -T _pl , ° C;

Δ T _f = T _f -T _pl , ° C;

T ₀ - temperature of thermal formation water, ° C;

T _PL - reservoir temperature, ° C;

T _f - phase transition temperature, ° C;

m is the porosity;

Δ N is the heat of the phase transition of gas hydrate, kcal / m ³ ;

α _guide - hydration coefficient (α _guide = 0.3-0.5).

In the process of development, they control the pressure of high-pressure thermal formation waters.

The proposed method, in comparison with the prototype, allows for effective thermal impact on the gas hydrate reservoir by high-pressure thermal waters of the underlying horizon with the expansion of the impact zone by transferring the thermal agent into horizontal wells located below and inside the reservoir. At the same time, the effect of expansion of the pore volume and cracks, decomposition of gas hydrates, which is achieved by a combined thermal and inhibitory effect, and, as a result, gas displacement and dissolution under the influence of pressure drop during the movement of the gas-saturated liquid front from bottom to top over the entire formation array, is observed.

In addition, this increases the chemical and thermal effects of the contacting surface of the mineralized thermal formation water. For example, an increase in the concentration of calcium chloride in thermal formation water by 1% reduces the equilibrium hydrate formation temperature by 0.5 ° C. In addition, thermal formation water with a high degree of mineralization has a heat capacity far exceeding that of fresh water.

The amount of high-pressure thermal formation water is regulated in accordance with the proposed formula, which allows the most efficient development of the reservoir without the risk of exceeding the reservoir pressure above the mountain, excluding the occurrence of uncontrolled hydraulic fracturing.

As a result of the influence of these factors, the degree of gas extraction on the scale of the whole reservoir increases significantly, especially in the case of hard to extract sources.

The proposed method is illustrated in the drawing, which schematically shows the location of the wells.

The method is as follows.

A bypass well 1 is drilled in the central part of a gas hydrate reservoir (GGZ) 2 to a formation with thermal high-pressure formation water (TVPV) 3 located below GGZ 2, then a horizontal well 4 is drilled under the sole of GGZ 2, into which TVPV 3 penetrates the entire formation GGZ 2. A horizontal well 5 is drilled from the overflow well 1 to the upper part of the GGZ 5 with a vertical outlet to the surface 6. As a result of the action of the TVPV on the GGZ, gas is taken from the horizontal well 5 and released to the surface through the vertical ny outlet 6, the downhole 5 is pressurized gas below the saturation pressure, which contributes to its efficient extraction.

An example of a specific implementation. Lavayozhskoye field, the reservoir of which contains a gas hydrate deposit.

The heat capacity of the rock is C _n = 600 kcal / m ³ · ° C; m = 0.2;

Δ N = 1.25 kcal / m ³ , α _guide = 0.4; T ₀ = 90 ° C; T _pl = 0 ° C; thermal capacity of thermal formation water With _T = 1000 kcal / m ³ · ° C, respectively

those. for the implementation of the method according to the invention it is necessary for each 1 m ³ rocks of approximately 0.178 m ³ thermal formation water. Since thermal formation water contains hydrate formation inhibitors and its temperature significantly exceeds the decomposition temperature of gas hydrate, cyclic injection of thermal formation water is possible.

Claims (2)

1. A method of developing a gas hydrate reservoir, including drilling bypass wells to a reservoir with terminal high-pressure waters, lying relative to the gas hydrate reservoir, with a horizontal branch under the sole of the gas hydrate reservoir to bypass the thermal high-pressure reservoir water from the underlying horizon into the overlying and subsequent gas production from deposits and drilling of gas vents with vertical outlet to the surface, characterized in that first in the central part the gas hydrate reservoir drills a bypass well to the formation with high-pressure thermal waters to supply formation water to the gas hydrate reservoir, branches off under the bottom of the gas hydrate reservoir with horizontal wells, then drill horizontal vents with the vertical amount of water to the surface of the gas hydrate reservoir with the vertical outlet to the surface formation water required for processing 1 m ^{3 of the} breed take

where q is the amount of thermal formation water required for processing 1 m ^{3 of} rock, m ³ ; With _p - the heat capacity of the rock, kcal / m ³ · ° C; With _t is the heat capacity of thermal formation water, kcal / m ³ · ° C; ΔT = T₀-T _pl ° C; T ₀ - temperature of thermal formation water, ° C; T _pl  - reservoir temperature, ° C; m is the porosity; Δ H is the heat of the phase transition of gas hydrate, kcal / m ³ ; α _guide  - hydration coefficient. 2. The method according to claim 1, characterized in that during the development process, the pressure of high-pressure thermal formation waters is monitored.