RU2081993C1 - Method for drilling-in of reservoirs - Google Patents

Abstract

FIELD: drilling of oil and gas holes. SUBSTANCE: method can be used for drilling-in of productive reservoirs in conditions of abnormally high reservoir pressure. According to method, in process of drilling, control is maintained of gas inflow to bore-hole. This consists in creation of hydraulic pressure pulses on bottom hole or at bore-hole head and recording signals of pressure in tubes at head of bore-hole and in tube clearance. Equalized condition in bore-hole is maintained by increasing flow rate and/or density of drilling fluid until difference in time in receiving signals of pressure at bore-hole head with regular drilling fluid and in drilling fluid with additives. EFFECT: high efficiency.

Description

 The invention relates to the field of drilling oil and gas wells and can be used for opening productive formations in conditions of abnormally high reservoir pressure.

A known method of opening the formation, including measuring the amplitude of the hydrodynamic pressure fluctuations in the annulus that occur when the bit is operated at the bottom, and its reduction by selecting the optimal flow rate of the drilling fluid according to the criterion of the minimum differential pressure in the well-formation system [1]
The disadvantage of this method is that the magnitude of the fluctuations in hydrodynamic pressures is measured using a depth gauge and this value becomes known after deciphering the diagram, which is extracted when lifting the drilling tool. In addition, it should be noted the technological complexity of the implementation of the specified method of opening the formations at equilibrium.

The closest technical solution of the known is the method of opening the formation, containing control over the flow of gas into the well, including the creation of hydraulic pressure pulses at the bottom or wellhead and recording pressure signals at the wellhead in the pipes and in the annulus [2]
The disadvantage of this method is that when gas is detected, drilling is stopped and drilling fluid is treated and degassed. However, not always reducing the density of the drilling fluid emerging from the annulus is dangerous. If the bottomhole pressure remains greater than the reservoir, then there is no reason to stop the drilling process.

 The invention is aimed at solving the problem of increasing the efficiency of the process of opening productive formations. In the implementation, the equilibrium conditions are maintained in the well-formation system.

где Δt_тек текущая разность времени прихода сигналов давления на устье скважины в обычном бурового раствора и в буровом растворе в присутствии флюида (нефти, газа), сек;
γ_p плотность бурового раствора, закачиваемого в скважину, на момент определения текущей разности времени, г/см³;
γ_o плотность бурового раствора, выходящего на устье скважины из затрубного пространства, на момент определения текущей разности времени, г/см³.To do this, in the method of opening the formation, including monitoring the flow of gas into the well, creating hydraulic pressure pulses at the bottom or wellhead and recording pressure signals at the wellhead in the pipes and in the annulus, the equilibrium state is maintained in the well by increasing the flow rate and / or density of the drilling the solution until the difference in the time of arrival of the pressure signals at the wellhead in the usual drilling fluid and in the drilling fluid in the presence of fluid (oil, gas) is reached

where Δt _{tech is the} current difference in the time of arrival of pressure signals at the wellhead in a conventional drilling fluid and in a drilling fluid in the presence of fluid (oil, gas), sec;
γ _{p the} density of the drilling fluid injected into the well, at the time of determining the current time difference, g / cm ³ ;
γ _{o the} density of the drilling fluid emerging at the wellhead from the annulus at the time of determining the current time difference, g / cm ³ .

As a result of numerous experimental studies conducted under conditions as close as possible to the actual drilling conditions in various geological conditions, a dependence is obtained that determines the maintenance of equilibrium in the well-formation system
Δt _tech. = 0.16 PH,
where Δt _tech. the current difference in the time of arrival of pressure signals at the wellhead in a conventional drilling fluid and in a drilling fluid in the presence of fluid (oil, gas), sec;
R is the local gas number;
H well depth, m

где R₀ газовое число в атмосферных условиях, R₀=Q г/Q ж;
Q_г расхода газа в атмосферных условиях, м³/сек;
Q_ж расход бурового раствора, м³/сек;
P₀ атмосферное давление, P₀=1 атм;
P давление, действующее на столб газированного бурового раствора, атм.

where R _{0 is the} gas number in atmospheric conditions, R ₀ = Q g / Q w;
Q _g gas flow in atmospheric conditions, m ³ / s;
Q _{W the} flow rate of the drilling fluid, m ³ / s;
P ₀ atmospheric pressure, P ₀ = 1 atm;
P pressure acting on a column of carbonated drilling fluid, atm.

Since at R ₀ ≅1, even if the entire well is filled with a gas-liquid mixture, the position of unstable equilibrium does not occur.

Подставляя вместо

и вместо

где γ_p плотность бурового раствора, заключаемого в скважину, на момент определения текущей разности времени, г/см³;
γ_o плотность бурового раствора, выходящего на устье скважины из затрубного пространства, на момент определения текущей разности времени, г/см³,
получаем

В процессе непосредственного бурения на забое или устье скважины периодически возбуждают гидравлические импульсы давления. На устье скважины регистрируют сигналы давления в трубах и в затрубном пространстве с целью контроля за поступлением газа в скважину. О равновесном состоянии в системе скважина-пласт судят по разности времени прихода сигналов давления на устье скважины в обычном буровом растворе и в буровом растворе в присутствии флюида (нефти, газа). Равновесному состоянию соответствует величина разности времени, определяемой из соотношения

где Δt_тек. текущая разность времени прихода сигналов давления на устье скважины в обычном буровом растворе и в буровом растворе в присутствии флюида (нефти, газа), сек;
γ_p плотность бурового раствора, закачиваемого в скважину, на момент определения текущей разности времени, г/см³;
γ_o плотность бурового раствора, выходящего на устье скважины из затрубного пространства, на момент определения текущей разности времени, г/см³.From here

Substituting instead

and instead

where γ _{p the} density of the drilling fluid enclosed in the well, at the time of determining the current time difference, g / cm ³ ;
γ _{o the} density of the drilling fluid emerging at the wellhead from the annulus, at the time of determining the current time difference, g / cm ³ ,
we get

During direct drilling at the bottom or wellhead, hydraulic pressure pulses are periodically excited. At the wellhead, pressure signals are recorded in the pipes and in the annulus to control the flow of gas into the well. The equilibrium state in the well-reservoir system is judged by the difference in the time of arrival of pressure signals at the wellhead in a conventional drilling fluid and in a drilling fluid in the presence of fluid (oil, gas). The equilibrium state corresponds to the value of the time difference determined from the relation

where Δt _tech. the current difference in the time of arrival of pressure signals at the wellhead in a conventional drilling fluid and in a drilling fluid in the presence of fluid (oil, gas), sec;
γ _{p the} density of the drilling fluid injected into the well, at the time of determining the current time difference, g / cm ³ ;
γ _{o the} density of the drilling fluid emerging at the wellhead from the annulus at the time of determining the current time difference, g / cm ³ .

If the current time difference (Δt _tech ) exceeds the time difference (Δt) obtained from the above expression, the flow rate and / or density of the drilling fluid is increased until the Δt _tech value exceeds the Δt value.

В данном случае Δt_тек.= 12 сек. превышает Δt = 6,7 сек. что говорит о нарушении равновесного состояния в системе скважина-пласт. В зависимости от имеющихся возможностей осуществляют увеличение расхода и/или плотности бурового раствора. Данную операцию проводят до тех пор, пока значение Δt_тек не достигнет величины, не превышающей 6,7 сек.The process of drilling a well is carried out and the drilling fluid is circulated with a density of p = 1.4 g / cm ³ . Periodically (after 10-15 minutes), hydraulic pressure pulses are excited at the bottom of the well or wellhead and the current values of the difference in the time of arrival of pressure signals at the wellhead in the pipes and annulus are determined. The current time difference Δt _tech = 12 seconds is fixed. In this case, we determine the density of the drilling fluid emerging at the wellhead from the annulus γ _o == 0.5 g / cm ³ . Substitute the source data into the expression

In this case, Δt _tech. = 12 sec. exceeds Δt = 6.7 sec. which indicates an imbalance in the well-reservoir system. Depending on the available capabilities, an increase in the flow rate and / or density of the drilling fluid is carried out. This operation is carried out until the Δt _tech value reaches a value not exceeding 6.7 seconds.

Claims (1)

The method of opening the formation, including monitoring the flow of gas into the well, creating hydraulic pressure pulses at the bottom or wellhead and recording pressure signals at the wellhead in the pipes and in the annulus, characterized in that the equilibrium state in the well is maintained by an increase in flow rate and / or density the drilling fluid until the difference in the time of arrival of pressure signals at the wellhead in the normal drilling fluid and in the drilling fluid in the presence of fluid is reached

where Δt _{tech is the} current difference in the time of arrival of pressure signals at the wellhead in a conventional drilling fluid and in a drilling fluid in the presence of fluid, s;
γ _{p the} density of the drilling fluid injected into the well at the time of determining the current time difference, g / cm ³ ;
γ _{o the} density of the drilling fluid emerging at the wellhead from the annulus at the time of determining the current time difference, g / cm ³ .