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A Calculation Method of Bottom-hole Sand Settling During Offshore Natural Gas Hydrate Drilling and Production

A calculation method and natural gas technology, which is applied in the direction of earthwork drilling, measurement, and fluid extraction, can solve the problems of jet drilling tools being stuck, stop production, and affect the effect of jet fragmentation, etc., to achieve easy operation, reliable principle, and avoid safety accidents Effect

Inactive Publication Date: 2022-04-15
SOUTHWEST PETROLEUM UNIV +2
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] During the gas hydrate jet fragmentation drilling process, if some hydrate deposits do not return along the wellbore annulus with the jet fluid, they will gradually accumulate at the bottom of the well, and then form bottom-hole sand sedimentation. A large amount of mud and sand deposits will affect the The jet fragmentation effect reduces the recovery rate of natural gas hydrate, and even causes major accidents such as jet drilling tools being stuck and buried, affecting production and even leading to production shutdown

Method used

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  • A Calculation Method of Bottom-hole Sand Settling During Offshore Natural Gas Hydrate Drilling and Production
  • A Calculation Method of Bottom-hole Sand Settling During Offshore Natural Gas Hydrate Drilling and Production
  • A Calculation Method of Bottom-hole Sand Settling During Offshore Natural Gas Hydrate Drilling and Production

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Experimental program
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Embodiment 1

[0033] Step 1, take a set of data as an example. Known volume coefficient B of natural gas hydrate decomposition hyd =164, the volume flow Q of the natural gas returned from the annular wellhead g1 (t) = 0.4445m 3 / s, the equivalent volume flow rate of natural gas Q g2 (t) = 0.323m 3 / s, the mud and sand flow rate Q returned from the annular wellhead sr (t) = 0.00705m 3 / s; Reservoir porosity Ф = 0.3, gas hydrate volume coefficient η = 0.8 in the pores;

[0034] Step 2, calculate the solid-state equivalent volume flow rate of the decomposed gas hydrate in the annular space:

[0035] Step 3, calculate the solid-state equivalent volume flow rate of gas hydrate returned from the annular wellhead:

[0036] Step 4, calculate the volume rate of solid-phase gas hydrate entering the wellbore annulus: Q hyd (t)=Q hyd1 (t)+Q hyd2 (t)=0.00467987804m 3 / s;

[0037] Step 5, calculate the volume rate of mud and sand entering the wellbore annulus:

[0038] Step 6, calcul...

Embodiment 2

[0041] Taking part of the working condition data as an example, the volume coefficient B of natural gas hydrate decomposition is known hyd =164. The porosity of the reservoir is Ф=0.3, and the volume coefficient of gas hydrate in the pores is η=0.8. Some working condition data are shown in Table 1.

[0042] Table 1 Partial working condition data and results

[0043] time / s Q g1 (t)m 3 / s

[0044] Apply the calculation method described in the present invention, obtain the relation of bottom-hole sedimentation rate and exploitation time such as figure 1 As shown, the relationship between the bottom hole sand volume and the production time is as follows: figure 2 As shown, the bottom hole sand volume increases with the increase of production time.

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Abstract

The present invention relates to a method for calculating the amount of sand settling at the bottom of a well during the drilling and production of marine natural gas hydrate. The solid-state equivalent volume flow Q of the volume flow of natural gas returned from the empty wellhead hyd1 (t); step 3, calculate the solid-state equivalent volume flow rate Q of natural gas completely decomposed by the hydrate particles returned from the annular wellhead hyd2 (t); step 4, calculate the gas hydrate solid equivalent volume flow rate Q in the process of drilling and production hyd (t); step 5, calculate the volume rate Q of mud sand contained in the wellbore annulus s (t); Step 6, calculating the bottom-hole sand settlement rate Q ss (t); Step 7, calculating the bottom sand volume V ss (t), that is, the amount of sand at the bottom of the well at the specified mining time. The invention can conveniently calculate the bottom-hole sand sedimentation amount of the marine natural gas hydrate layer during the jet fragmentation process under the on-site construction conditions, so as to provide a basis for safe drilling and avoid safety accidents.

Description

technical field [0001] The invention belongs to the technical field of marine natural gas hydrate drilling and production, and in particular relates to a calculation method for the amount of sand sedimentation at the bottom of a well during the drilling and production of marine natural gas hydrate. Background technique [0002] Natural gas hydrate is a clathrate crystal compound that exists stably in low temperature and high pressure environment, commonly known as "combustible ice". As a new type of clean energy, it is considered to be the most potential alternative energy in the 21st century. It has the remarkable characteristics of high gas storage density, high calorific value, and wide distribution range. It is mainly distributed in the low-temperature and high-pressure environment of land permafrost and the ocean around the continental margin. The marine gas hydrate resources are about more than 100 times. Aiming at the development of marine natural gas hydrates, as a...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): E21B47/00E21B49/00E21B43/01G06F17/10
CPCE21B47/00E21B49/00E21B43/01G06F17/10
Inventor 魏纳张超赵金洲张烈辉周守为李清平朱军龙王晓然
Owner SOUTHWEST PETROLEUM UNIV
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