RU2697438C1 - Method of well control under conditions of inertial effect at primary opening of productive oil-gas-saturated stratum - Google Patents

Abstract

FIELD: drilling of soil and rocks; mining.SUBSTANCE: invention relates to drilling of oil and gas wells, namely to well control under conditions of absorption and manifestations in productive oil and gas-saturated formation, and can be used in drilling and development of oil, gas and industrial brines (brine). Proposed method comprises primary opening of productive oil-and-gas-saturated formation by drilling in conditions of full absorption of flushing fluid. At the same time from the moment of occurrence of absorption at drilling, continuous automatic refilling of the well is performed with the applied drilling fluid in annular space with output of 3–5 l/s in order to compensate for the negative difference between the static and dynamic levels, without allowing the well's rapid transition from absorption to gas-oil-and-water development. When lifting the drilling tool with piston, the well is refilled with the applied drilling fluid in the annular space by means of the cementing unit through each 100 m in the volume of the lifted metal of the drill pipes plus 0.3 m.EFFECT: enabling the process reliability of drilling at the stages of exploration and development of brine, oil and gas deposits.1 cl, 4 dwg

Description

The invention relates to the field of drilling oil and gas wells, and in particular to well control under conditions of absorption and occurrence in a productive oil and gas saturated formation, and can be used in drilling and development of oil, gas and industrial brines (brines).

One of the problems that arise when drilling deep wells for oil and gas in difficult geological conditions associated with the initial opening of an abnormally high-permeable carbonate oil and gas saturated reservoir with an abnormally low reservoir pressure is the sudden transition of the well from the mode of absorption of the drilling fluid into the mode of oil and gas development. The mechanism of occurrence of absorption is due to a number of factors, such as low reservoir pressure and high reservoir permeability [Polyakov VN, Ishkaev RK, Lukmanov RR Technology of completion of oil and gas wells. - Ufa: Tau. - 1999. - 408 p.]. Absorption occurs both in the upper and in the productive part of the geological section of the wells. The nature of each absorption imposes additional restrictions on the well drilling process. Absorption in the upper part of the section, as a rule, does not lead to consequences associated with gas and oil manifestations from the reservoir. In turn, the occurrence of acquisitions in productive formations is associated with a number of risks and dangers, including for the health and life of the personnel of drilling crew workers. A complicating factor is the specific features of cavernous-fractured carbonate reservoirs. The developed fracturing system, differences in the reservoir properties of the reservoir rock within the same field, the stress state of the reservoir rock — all this imposes additional restrictions on the design of the development of deposits in carbonate systems [Kutukova NM, Birun EM, Malakhov R.A et al. Conceptual model of the structure of the Riphean natural reservoir of the Yurubcheno-Tokhomskoye field // Oil industry. 2012. No. 11. S. 4-7].

In practice, drilling wells in oil-and-gas-saturated reservoirs with abnormally low reservoir pressure has rather unpredictable consequences of the phenomenon known as the inertial effect [Semenov N.Ya. Research and isolation of absorbing and water-producing strata: a manual for a process engineer for drilling wells: at 2 p.m. / N.Ya. Semenov. - Ufa: BashNIPIneft, 2010-2014. - 900 s. and etc.]. When drilling wells in Eastern Siberia, in particular, in the Krasnoyarsk Territory, complications arising from the inertial effect are encountered regularly and can result in long-term liquidations of gas and oil and gas occurrences.

In the above sources there are no recommendations for drilling wells in oil and gas saturated formations under the conditions of inertial effect with complete absorption of flushing fluid.

Closest to the claimed method relates to the primary opening of a complex cavernous-fractured carbonate oil and gas saturated formation with a long horizontal wellbore [Patent No. 2598268 of October 13, 2016 (Prototype)]. This patent describes the possibility of drilling wells with simultaneous absorption and development.

This method has a disadvantage associated with the fact that it does not contain the complex of necessary operational measures performed with the complete absorption of flushing fluid in the well under the conditions of inertial effect. It does not contain recommendations for hoisting operations with full absorption and the procedure for the occurrence of complete absorption during drilling under the conditions of inertial effect to prevent the transition of the well into development mode.

In a simplified form, the inertia effect phenomenon can be described as follows:

When drilling without absorption:

where Rgst is the hydrostatic pressure of the drilling fluid, Rpl is the reservoir pressure, 1.05 is the safety factor according to the Safety Rules of the oil and gas industry

When complete absorption occurs without an inertial effect

When complete absorption occurs under conditions of an anomalous highly permeable collector, taking into account the inertial effect

where Rinerz is the pressure of inertia ("inertial effect")

Therefore, after the inertial effect disappears (part of the volume of the drilling fluid went into the formation for absorption), an imbalance with the formation occurs

In other words, all the hydrodynamic conditions for the start of GNPP from an abnormal highly permeable reservoir are created. Compensation of the inertia pressure is necessary; otherwise, gas and oil and gas phenomena or other more serious consequences cannot be avoided.

The objective of the claimed method is the development of an effective technology for drilling wells in oil and gas saturated formations under the conditions of inertial effect with complete absorption of the flushing fluid.

The technical result is the technological reliability and safety of drilling wells for oil and gas in difficult mining and geological conditions.

The problem is solved by the proposed method of controlling a well under the inertial effect during the initial opening of a productive oil and gas saturated formation, including the initial opening of a productive oil and gas saturated formation by drilling under conditions of complete absorption of the drilling fluid, characterized in that from the moment of occurrence of absorption during drilling, the well is automatically refilled with the used drilling fluid in annular space with a productivity of 3-5 l / s in order to compensate for the negative the difference between the static and dynamic levels, preventing a quick transition of the well from absorption to gas and oil manifestations, and when lifting a drilling tool with a piston, the well is used to be added to the annulus using a cementing unit every 100 m in the volume of the raised metal of the drill pipe plus 0.3 m ³ .

As a rule, the dynamic level during drilling with absorption is fixed higher than the static level. Under standard conditions, this occurs due to the creation of additional dynamic pressure on the formation and the backward reaction of the formation associated with an increase in the resistance of the formation when the washing fluid is injected into it.

In practice, a phenomenon called the inertial effect has occurred. It has been described by many researchers, including N.Ya. Semenov. This effect was explained by the fact that the cross-sectional area during the transition from the trunk of the vertical section — the wellbore to the horizontal section — the formation increases significantly, resembling a sudden expansion. After this, the flow in the reservoir enters the expanding pipeline - confuser. In this case, a very large volume of fluid is set in motion, located in the well and around it at a great distance in the formation, acquiring the corresponding inertia of movement, which contributes to an increase in the suction effect.

The essence of the invention: maintaining the required static level of flushing fluid when drilling a well through an oil and gas saturated formation under conditions of inertia effect with complete absorption of flushing fluid.

EXAMPLE

As an example, data on wells drilled in the north of the Krasnoyarsk Territory are given. After opening the absorption zone associated with the opening of a highly permeable vertical crack in a productive oil and gas saturated reservoir, drilling is carried out without circulation. When the drilling process is stopped, preventive topping up of the well in the annulus is carried out. After technical parking, a static level of 250 m is fixed (Fig. 1).

Well condition:

An absorption zone is opened, drilling is stopped. The static level was repulsed at Nst = 250 m. The well is in equilibrium with reservoir pressure under static conditions.

Further drilling continues with complete absorption. Not only the injected fluid, but also the fluid from the annular space goes into the reservoir. The dynamic level in the well is fixed at around 300 m (Fig. 2)

Well condition:

Absorption drilling. Ndin = 300 m. The well is in equilibrium with reservoir pressure in dynamic conditions.

Further drilling continues with complete absorption. Not only the injected fluid, but also the fluid from the annular space goes into the reservoir. The dynamic level in the well is fixed at around 300 m.

Well condition:

Stop drilling a well. Ndin = 300 m. Instant transition of a well from an absorbing well to a gas and oil and gas producing (GNP). Imbalance of the well. Hydrostatic pressure is less than reservoir pressure. Formation fluid and drilling fluid begin to rise rapidly through the annulus of the well.

When drilling with absorption stops, the well almost immediately goes into development mode, which is precisely due to the difference between the dynamic (Ndin = 300 m) and the static level (Nst = 250 m). The inertia of a large mass of fluid from the formation begins to accelerate toward the well, contributing to additional backwater from the side of the formation (Fig. 3).

Well condition

Stop drilling a well. Ndin = 300 m. Instantaneous transition of a well from an absorbing well to GNP. Imbalance of the well. Hydrostatic pressure is less than reservoir pressure. Formation fluid and drilling fluid begin to rise rapidly through the annulus of the well.

As one of the rather serious complications associated with the inertial effect, we can give an example, in Fig. 4., which shows that when two drainage cracks are opened, the process of gas-oil-water manifestation and absorption occurs simultaneously. In such conditions, it is impossible to continue drilling. When the circulation stops, the well goes into the gas-oil and gas manifestation mode, when trying to shut it down (with the blowout equipment closed), all injected fluid goes to absorption. Well condition:

Two vertical cracks were opened. The balance in the well is broken. The drilling fluid pumped through the drill string absorbs the second open fracture. In this case, the overlying crack begins to manifest.

Claims (1)

A method of controlling a well in an inertial effect during the initial opening of a productive oil-and-gas-saturated formation, including the initial opening of a productive oil-and-gas-saturated formation by drilling under conditions of complete absorption of the drilling fluid, characterized in that from the moment of occurrence of absorption during drilling, the well is automatically added to the annulus with drilling fluid used in the annulus with a productivity of 3-5 l / s in order to compensate for the negative difference between the static them and dynamic levels, preventing a quick transition of the well from absorption to gas and oil and gas, and when lifting a boring tool with a piston, the well is used to be added to the annulus using a drilling fluid with a cementing unit every 100 m in the volume of the raised metal of the drill pipe plus 0.3 m ³ .

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