RU2419717C1 - Procedure for fan-like interval-by-interval operation of oil producing wells - Google Patents

Abstract

FIELD: oil and gas production. ^ SUBSTANCE: procedure consists in drilling pressure boreholes and multi-hole producers with horizontal arrangement of boreholes in region of payout bed wherefrom fluid is withdrawn. According to the invention side boreholes, horizontal in the payout bed, are arranged symmetrically in radial direction relative to the main borehole. Fluid is withdrawn from wells cyclically from each interval starting from the last drilled side horizontal borehole and ending with the main borehole. Also, fluid is withdrawn from each interval of the bed drained with the main and side horizontal boreholes till current bed pressure drops to 60-80% from initial or till water cut in withdrawn product rises to 100%. Repetition of cycles and well operation are terminated upon complete exhaustion of oil reserves from the part of the payout bed drained with these wells. ^ EFFECT: raised yield of oil from beds with non-uniform permeability and reduced expenditures for drilling operations. ^ 2 dwg

Description

The invention relates to the oil industry, in particular to the field of development and exploitation of oil fields by multilateral horizontal wells.

One of the most effective ways to increase well productivity is to lay horizontal sidetracks in low-productivity or idle wells. To reduce the number of wells during field development and reduce the cost of their construction, the method of multi-hole drilling is used [1, pp.21-24]. The essence of the method lies in the fact that from the main wellbore, after its attachment, sidetracks are drilled. The number of sidetracks and their location depend on the geological features of the formation and its physical characteristics.

Of the known technical solutions closest to the claimed method, which is also the base, is a method of developing a multilayer heterogeneous oil field with branched horizontal wells [2]. The essence of the known method [2] is that when drilling horizontal and / or subhorizontal shafts, the boundaries of zones with different permeability intersected by these shafts are determined, the number of branches is determined from the condition of ensuring uniform development of field reserves. A packer is installed at the border of zones differing in permeability by 1.5 and more times, and the selection of products is carried out using equipment of simultaneous-separate operation while maintaining bottom-hole pressure for each selected zone.

The disadvantage of this method [2] is the insufficient development of oil reserves in reservoirs heterogeneous in permeability. Firstly, because of the random distribution of zones with different permeabilities along the strike and section, which can differ by tens of times and interlayer many times along the wellbore, it is impossible to unambiguously determine the boundaries of zones differing in permeability by 1.5 or more times for installing the packer . Secondly, pulling water to the wellbore in the area of perforation along the most permeable interbeds will lead to the blocking of oil-saturated interbeds and zones with lower permeability and a rapid increase in water cut of produced products.

The aim of the proposed method is to increase oil recovery heterogeneous permeability of the formations and reduce the volume and cost of drilling.

This goal is achieved by the fact that an oil field with a heterogeneous permeability reservoir is drilled with a rare grid of wells. Each well has a main wellbore, at the end of which it is perforated in the area of the reservoir, examined for inflow and a packer is installed. From the main trunk above the reservoir, insert the first side trunk, horizontally directed in the field of the reservoir. At the end of drilling, it is also examined for inflow and a packer is installed. Then similarly sequentially insert other sidetracks horizontally directed in the field of the reservoir. The horizontal sections of all sidetracks located in the reservoir are directed symmetrically in the radial direction relative to the main wellbore. The number of sidetracks depends on the average permeability of the developed formation. After completion of the drilling of the last lateral horizontal well, it is also perforated, examined for inflow and the optimal flow rate is determined. A submersible pump is lowered into the well and the well is operated. The fluid is taken from the last horizontal wellbore, the flow rate of the liquid, the pressure at the bottom and the water cut of the produced fluid are controlled. If during operation the fluid flow rate decreases, i.e. injection wells do not provide pressure recovery in the reservoir, or a sharp increase in water cut of produced products occurs, i.e. pumped water reached the wellbore, then the selection of fluid from the last horizontal wellbore is stopped. At the insertion point of the last horizontal trunk, a packer is installed. From the penultimate horizontal well, the inset of which is located below the last horizontal well along the axis of the main well, the packer is removed and fluid is sampled, controlling fluid flow rate, downhole pressure and water cut in produced fluid. At the same time, in the drainage interval circuit of the last horizontal wellbore, from which liquid withdrawal was stopped, there is a gradual restoration of pressure and redistribution of saturations, which tend to an equilibrium phase distribution in the pore space. In a similar manner, the following horizontal trunks are connected in series and the liquid is taken from them. At the final stage of the cycle of interval fan operation, the packer is removed from the main wellbore and fluid is taken from the drainage circuit of the formation zone immediately adjacent to the main wellbore. During this period of time, the pressure and the equilibrium distribution of phases in the pore space of the formation are restored in the reservoir intervals previously drained by the laterally horizontal trunks of the formation. Next, the packer is installed on the main wellbore, the packer is removed from the last lateral wellbore (from which the well began to operate) and fluid is sampled, controlling fluid flow rate, bottomhole pressure and water cut of produced fluid. The entire cycle of fan-interval interval operation of a multilateral well is repeated in the same sequence. Well operation is stopped after the maximum possible development of oil reserves from the productive part of the formation drained by this well.

It is the sequential fan interval production of the reservoir with the repetition of cycles to the maximum possible development of oil reserves from the reservoir is the essence of the invention.

Thus, the claimed method meets the criteria of the invention of "novelty." When studying other technical solutions in this technical field, the features that distinguish the claimed invention from the prototype were not identified and therefore they provide the claimed technical solution with the criterion of "significant differences".

The technical essence of the invention is illustrated by projections of a multilateral well on the vertical plane (profile) of FIG. 1 and on the horizontal plane (plan) of FIG. 2.

Figure 1 shows the profile of a multilateral well, consisting of a main trunk 1 and sidetracks 2, horizontally directed in the field of the reservoir. At the entrance of the main trunk 1 to the reservoir and on the branches of the side trunks, packers 3 are installed.

Figure 2 shows the plan of a multilateral well, consisting of the main wellbore 1 and sidetracks 2-9, horizontally located in the radial direction in the field of the reservoir. The dashed line shows the drainage contours of the intervals of the reservoir by the main and side trunks.

The proposed method of fan-wise interval operation of oil wells is implemented as follows. After drilling a multilateral well, consisting of a main well and sidetracks with a horizontal direction in the area of the reservoir (Figs. 1 and 2), a submersible pump is lowered into the well and fluid is selected in accordance with the inflow studies. The selection of fluid begins from the last drilled lateral trunk. All other entrances to the main and side trunks are closed by packers. This allows drainage of the interval, i.e. parts of the reservoir.

There are a large number of oil fields with complex reservoirs, in which interlayers with very different permeability alternate. The development of such fields is complicated by the fact that a large number of wells are being decommissioned due to a decrease in reservoir pressure and their rapid flooding. It is known that over time there is a restoration of reservoir pressure and redistribution of saturations in the pore space of the reservoir. Therefore, technologies for operating oil wells in a batch mode are being introduced [3, 4]. Fan-based interval operation of oil producing wells takes into account the peculiarities of developing fields with complex reservoirs.

The fluid is taken to reduce the current reservoir pressure to 60-80% of the initial [4] or increase the water cut to 100%. When one of these conditions is reached, the selection of liquid from the last drilled lateral barrel is stopped and the packer is installed in it. Then, in a similar manner, sequentially carry out the selection of fluid from other sidetracks that drain other intervals of the reservoir. At the final stage of the fan-interval interval operation, the packer is removed from the main wellbore and fluid is taken from the drainage circuit of the formation zone immediately adjacent to the main wellbore. During this period of time in the reservoir intervals previously drained by the sidetracks, reservoir pressure and the equilibrium distribution of phases in their pore space are restored. Upon completion of the selection of fluid from the main trunk, i.e. when one of the conditions is achieved: a decrease in the current reservoir pressure to 60-80% of the initial one or an increase in water cut to 100%, a packer is installed in the main trunk. Next, the entire cycle of fan-interval interval operation of a multilateral well is repeated in the same sequence. Operation of the well is stopped after the full development of oil reserves from part of the reservoir, drained by this well.

Using the proposed method for fan-wise interval operation of oil wells provides the following advantages compared to existing known methods.

1. Consistent interval production of a part of a productive formation drained by a multilateral well, with the repetition of cycles, allows to increase the coverage of heterogeneous permeability formations, increase the uniformity of oil reserves production from them and thereby ensure the maximum possible production of oil reserves.

2. An oil field with a heterogeneous permeability reservoir is drilled with a rare grid of wells. The cost of building branched horizontal wells is 1.6 times higher than the construction of vertical wells [1, p.23]. The specific investment per 1 ton of oil produced from branched horizontal wells is 2.2 times less than for vertical wells. Economic efficiency significantly exceeds the initial cost of building branched horizontal wells.

Information sources

1. Features of oil and gas production from horizontal wells. / Ed. G.P. Zozuli. - M.: Publishing Center "Academy", 2009. - 176 p.

2. Patent RU No. 2339801. Published November 27, 2008. A method of developing a multilayer heterogeneous oil field with branched horizontal wells / Abdulmazitov R.G., Ramazanov R.G., Yamgutdinov M.R. and etc.

3. Patent RU No. 23389800. Published November 27, 2008. The method of development of oil deposits / Abdulmazitov R.G., Ramazanov R.G., Ziyatdinov R.Z. and etc.

4. Tyapov O.A., Garifullin A.R., Basov S.G., Khanzhin V.G. Modern control systems for submersible electric pumps during periodic well operation modes. // Oil industry, 2008, No. 2, p. 94-96.

Claims (1)

A method of fan-wise interval operation of oil producing wells, including drilling injection wells and producing multilateral wells with a horizontal location of the shafts in the field of the reservoir, from which the selection of fluid, characterized in that the location of the side shafts horizontal in the reservoir, is symmetrical in the radial direction relative to the main trunk and the selection of fluid from the wells is carried out cyclically at intervals starting from the last drilled lateral horizon the borehole and ending with the main bore, moreover, fluid is taken from each interval of the reservoir drained by the main and lateral horizontal boreholes until the current reservoir pressure is reduced to 60-80% of the initial or increase in water cut of the produced product to 100%, cycle repetition and well operation stop after the full development of oil reserves from part of the reservoir drained by these wells.

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