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V. I. Nikishov (OAO "NK “Rosneft"), A. I. Markin, R. R. Gabdulov (OOO "RN-Yuganskneftegaz"), P. I. Slivka (OOO "RN-YufaNIPIneft")

Introduction
The field development using combined methods of exploitation of layers and creating a reliable control and regulation system of processes of production of reserves with respect to every layer is one of the main postulates of mining laws and regulations during the projection of development. Therefore at present time high emphasis is placed on technologies including the use of wells with multi-packer section arrangements designed for differential injection in geological heterogeneous production facilities [1].

Currently existing constructions of arrangements for dual injection operations (ORZ) in wells uncovering three and more layers prevent from determination of liquid flow rate of every layer without participation of the workover crew. The injection into layers is regulated after study of geophysical data and data according to well performance for a specified period of time.

The basic idea of the submitted article is the systematisation of regulation and control of the development of multilayer fields using the ORZ system. The ultimate aim is the transition to an intelligent well which enables to regulate the working conditions of layers in real-time environment and to ensure differentiated action in separate interval or area of oil reservoir.

Basic line of improvement of multi-packer arrangements ORZ
The targeted aim can be achieved at the expense of the creation of tandem of the existing technology ORZ, use of control sensors of bottom-hole parameters (pressure p and temperature T) as well as software engineering for the calculation of liquid flow rate according to the available data of pressure decrease which is the "nervous system" of the intelligent structure [2].

The following refers to the improvement elements of the construction of arrangement ORZ (fig. 1):

1. Construction modification of the bottom-hole flow bean which enables to reduce the hydraulic resistance for the purpose of increase of its throughput capacity.

2. Determination of liquid flow rate based on the calculation principle of liquid according to pressure decrease and as a consequence the creation of a software product for the calculation of liquid flow rate for injection into the layer.

3. Use of geophysical sensor systems (p, T) within the tube and the annular space of the arrangement ORZ with information transfer to the surface via cable lines.

We examine one of the main improvement elements of multi-packer system of the ORZ system. As shown in practice the liquid flow rate through a flow bean of the existing construction is limited by the diameter of the axial channel. It is possible to achieve a large flow rate through the flow bean for the guarantee of the planned regime of injection capacity by enlarging the diameter (construction modifications) of the axial channel or reducing the pressure decrease at the existing construction.

Figure 1 shows comparative schemes of the arrangement ORZ in use (a) and the improved arrangement ORZ (b).



Fig. 1. Schemes of the arrangement ORZ in use (a) and the improved arrangement ORZ (b)

For analyse it is recommended to compare two versions of flow bean construction with different types of orifice instruments (SU) (table 1).

The orifice instruments in the form of Venturi tubes make it possible to increase the throughput capacity of the flow bean at the expense of the reduction of decrease in pressure by the overcoming resistance to the fluid stream. It can be accepted that the fractional decrease in pressure is 5 - 20 % for Venturi tubes generally.

In case of flow motion the friction head loss lengthwise and the overcoming local resistance is often observed at the same time. The total head loss is determined as arithmetic loss sum of these types.

The hydraulic calculation is presented for flow beans of the existing construction (in the form of a restricted channel) and in the form of Venturi tubes. Due to small sizes and high seed of the liquid stream the following assumptions can be added to the calculations:

- the existing flow bean represents an orifice plate of a wide, even lengthwise restricted part of the channel;

- the friction pressure loss is equal to zero.





The theory about the liquid flow through nozzles supposes that the average speed of the stream increases together with its restriction and the static pressure becomes less than the static pressure before the orifice plates/Venturi tubes. The pressure difference (differential pressure) becomes higher if the flow environment increases. So it can serve as flow measure [3-5]. Table 2 shows the methodology algorithm of the flow bean at differential pressure.

The use of the flow bean in arrangements ORZ is limited by the size of the flow area of 9.5 mm. The use of orifice instruments in the form of Venturi tubes under equal conditions makes it possible to increase the liquid flow rate through the flow bean up to 39%. Table 3 shows a comparative calculation of two versions of flow bean.



Employing the trail-and-error method of number values, i.e. changing the diameter of the existing flow bean it is easy to calculate the equivalent diameter (11.56 mm) of the restrictive channel which would guarantee a liquid flow rate of 659.28 m3/day. The result of the calculations is the dependence of the liquid flow rate on the differential pressure for two versions of flow bean.

Figure 2 shows that the flow bean in the form of Venturi tubes has a higher throughput capacity in comparison to the flow beans in use. Charts which are shown in figure 3 are used for the sake of simplicity of determination of the liquid flow rate for different flow bean diameters and the value of differential pressure. The throughput capacity of the flow bean does practically not depend on the production material of the orifice instruments and measuring pipe and depends largely just on the surface finish characteristics, the wear-resistant and corrosion behaviour of the materials. An alternative solution for the increase of throughput capacity for the Priobsk field is often the use of an extension pipe without a



Fig. 2. Dependence of the liquid flow rate on the differential pressure for Venturi tubes (1) and orifice plates (2)



Fig. 3. Charts for determination of the liquid flow rate through the flow bean in the form of Venturi tubes (measuring pipe diameter - 20 mm; material of SU and the measuring pipe - 40X)

borehole chamber and cap. However, the given solution is in conflict with the company specification concerning the engineering requirements on the organisation ORZ of water at the Priobsk field in the injection wells which uncovered several sites (No. P1-01 S-034 JuL-99) according to which the following tests must be carried out after the first running-in and installation of equipment in the well for the separate water injection:

1. pressure test of the oilwell tubing columns;
2. reliability control of the performance of packers in terms of lack of fluid crossflow;
3. regulation operations with a view to ensuring the planned injection conditions including the performance of geophysical studies.

Another important constituent of pressure loss in the construction of flow bean is the presence of local resistance occurring in zones of tube section changes or travelling direction of the liquid stream. This loss depends on the average speed and the cross-sectional dimensions of fluid jet, forms and sizes of the barrier, its placing in relation to the fluid jet.

Taking into account the consistency of mass of the liquid flow rate and neglecting the friction hydraulic resistance the Weisbach formula can be used for the determination of local loss [6-7]

∆p = ξ ,

where ξ – local pressure loss; p - fluid density; v - average speed (as a rule after the pass-through through the local resistance).

The determined theoretical coefficient values of local resistance for a number of cases (sudden contraction, orifice plate, etc.) comply with the test data completely.

For the purpose of adaptation of the calculation procedure of the flow bean autonomous pressure sensors in the arrangements ORZ which make it possible to register pressure in annular space (between the production string and the arrangement ORZ) were installed in the well 6295 of the Priobsk field on 22 June 2008. The pressure in the tubes (before the entry into the flow bean) and the actual flow were determined according to the field geophysical survey. For the complete adaptation of the calculation methodology it is necessary to have statistics of the survey under different conditions.

The largest resistance becomes evident in the case of peg-leg of liquid stream. When using the flow bean where the liquid changes the direction by 90º abruptly after having left the orifice instruments the pressure decrease is 6.29 MPa, then the pressure decreases 3 times like before the exit at an angle of 45º. As a result small changes to the construction of the flow bean were recommended; in particular the directions of the liquid entry and exit out of the flow bean have changed (fig. 4).

Body 1 of the regulating device is connected to the gripping head 2 and the tail 3. The tail 3 contains a gas lens 4. The gripping head 2 and tail 3 have sealing elements 5. The regulating device contains fluid passages, in addition, axial channels 6-8 are connected to side channels 9-11: in the tail are the axial channel 6 and the side channel 9, in the body are the channels 7 and 10 and in the head the channels 8 and 11 correspondingly.

Under the sealing elements and the gas lens is an axial channel which has restrictions 12, 13 by objective reasons. This is related to the fact that it is necessary to have space groove with some deepness for fastening of sealing rings 5 and a cementing collar of the gas lens 4.

For the reduction of resistance from restriction and the increase of its throughput capacity at the entry of restriction 14, 16 and exit of the restriction 15, 17 bevelled flowing wills 14-17 are installed which make it possible to minimise the internal hydraulic resistance what increases the throughput capacity, reduces the flow bean effect as well as the running time, reduces significant corrosion in the restriction zone.

The use of the recommended flow bean construction under equal conditions makes it possible



Fig. 4. Construction of a double-sided flow bean taking into consideration the integrated rework

to increase the liquid flow rate through the flow bean to 30-35% at the expense of loss reduction by overcoming the hydraulic resistance.

Another improvement direction of the arrangement ORZ is data acquisition from geophysical sensors on a real-time basis (see fig. 1). This project was initiated within the scope of the established working group Systems of New Technologies in the OAO HK "Rosneft". The introduced technologies ORZ in two layers and more than one well and with one downhole equipment has no analogue in the domestic and foreign oilfield practice. This work is carried out in wells with an internal diameter of the production string of 146 mm. The whole downhole equipment is drained of in one run.

At the moment at OOO "RN-Yuganskneftegaz" operations of the first stage of ORZ are carried out on the Priobsk field in the wells 8709/2016 and 7730/201a. The main tasks which will be decided during the performance of work are: lowering of the multi-packer section arrangement with sensors (p, T) in one run; acquisition of geophysical data (p, T) on a real-time basis; inspection of reliability of the entire system; detection and prevention of risks; transition to the final stage of "intellectualisation" of ORZ (fig. 5).

The stage-by stage approach of the operations is defined by the complexity of the operations to be carried out and the degree of intellectualisation of the well.

Conclusion
1. The current development state of the majority of multilayer fields is characterised by the ever-increasing demand for the use of technologies which make it to maintain separate account of products to be lifted and to be injected.

2. The improvement of technology ORZ is based on the creation of tandem of the existing technologies of geophysical control of layer parameters and the mathematical devices of calculation of hydrodynamic processes taking place at the boundary of well - layer.

3. The changes to the existing arrangement must relate to all elements of the system ORZ. At OOO "RN-Yuganskneftegaz" in association with OOO NPO "Novye Heftyanye Tekhnologii" a flow bean was developed which makes it possible to increase the flow rate to 30-35% in comparison to the flow beans used today.

4. Calculation methodology of the liquid flow rate according to the differential pressure is being developed jointly. According to the results of the collection of statistical material it is planned to develop a software product which makes it possible to carry out operational supervision of the flow bean operation without the involvement of geophysics.

5. At the moment operations are being carried out in the wells of Priobsk field. The performance of operations concerning the technological advancement of ORZ is divided in stages which are defined by the complexity of operations to be carried out and the degree of intellectualisation of the well.

6. A judgement must be passed on the economic efficiency of the implementation of the improved arrangement ORZ on the basis of the whole "life" cycle of the well.



Fig. 5. Transmitted-data circuit

However, the main effect of the project is linked to the raise of the coefficient of oil recovery to the expense of isolation of zones or intervals with harsh water breakthroughs.

7. The improvement of the technology ORZ is a relative recent trend both in Russia and abroad (in our situation in columns of 146 mm) due to lack of experience with the use of technology under real conditions. Therefore for this direction a more deepened approach is necessary in order to become an effective instrument concerning the control of water flood at multilayer fields. OOO "RN-Yuganskneftegaz" makes preparation for an adaptation of technology for two layer wells ("annular tube") which enable to maintain accounts of injected liquid immediately from the collar.

8. The improvement of technology ORZ is one step of the development of intellectualisation of oil production and differentiated water injection into heterogeneous geological objects. The company "Rosneft" is engaged in this at the moment.

List of references
1. Leonov V.A., Sharifov M.Z., Garinov O.M. ORRNEO Technology (Single Commingle Development of Several Production Zones) Introduction Experience on Oil Fields in Western Siberia/OOO NII "SibGeoTech"// SPE-104338

2. Lukyanov E.E., Kayurov K.N. Operation intellectualisation of injection and exploitation wells when using multi-packer arrangements for simultaneous injection and exploitation on multilayer wells//Karotazhnik. 2005. - No. 5. - p. 270-275.

3. GOST 8.586.1-2005 (ISO 5167-1:2003). Measurement of liquids and gases flow rate and quantity by means of orifice instruments. Part 1.

4. GOST 8.586.2-2005 (ISO 5167-2:2003). Measurement of liquids and gases flow rate and quantity by means of orifice instruments. Part 2.

5. GOST 8.586.4-2005 (ISO 5167-4:2003). Measurement of liquids and gases flow rate and quantity by means of orifice instruments. Part 4.

6. Rabinovich E.Z., Evgenyevich A.E., Hydraulics: 3rd ed. revised and amended. M.: Nedra, 1987. - 224 p.

7. Altshul A.D. Hydraulic resistance: 2nd ed. revised and amended. M.: Nedra, 1982. - 224 p.

Labels: Intelligent well completions, packers, Rosneft, Russia oil gas

posted by The Rogtec Team @ 14:28  2 Comments

Integra is one of the world's leading geophysical companies with over 40 crews operating in Russia and Kazakhstan as well as having an international presence. In Russia, the company's subsidiary, Integra Geophysics, is one of the leading companies by volumes acquired and Azimut Energy Services, it's Kazakhstan subsidiary, leads the industry in acquisition volumes. The company has acquired 2D and 3D seismic surveys for all of Russia's leading oil companies (Gazprom, Rosneft, LukOil, TNK-BP etc) and in Russia and Kazakhstan has a growing reputation with international oil companies like ENI, Shell, Chevron and BG after acquiring major 3D surveys over some of the world’s largest oil and gas fields.



Since 2006 Integra has been investing in new equipment and technology to improve health and safety (HSE) and operational performance. The result is that that the company is now equipped with some of the most advanced geophysical equipment available including a fleet of modern ION and Sercel vibrators and recording systems. This allows Integra to compete with some of the world's leading geophysical companies and implement technology routinely used in other areas of the world.

Heli-portable operations
In the summer of 2008 Integra Geophysics conducted a heli-portable seismic operation for TNK-BP in the Uvat region of West Siberia. The objectives of the survey were to improve operational efficiency, reduce the impact of seismic operations on the environment and test the viability of summer operations in areas where winter acquisition is the norm. Helicopter seismic operations are widely used in Canada and the USA to over come logistical challenges in mountainous terrains. Equipment is moved by helicopters thus reducing the need for heavy cross-country vehicles which can cause a long lasting impact on the environment.



The absence of helicopters suitable for heli-portable operations in Russia meant the company had to work closely with service provider UTair to acquire 2 AS350 helicopters and access Canadian pilots to train their Russian counterparts to conduct operations. Equipment required to carry large amounts of ground equipment and slings and hooks to allow helicopters to pick up equipment on the fly was also acquired. Restrictions on satellite receiver technology to help with positioning limited the full impact of operations.

The Uvat region is heavily forested and requires a significant amount of tree cutting. Typically shot and receiver lines are cut to a width of 4 metres to allow the passage of cross-country vehicles and tree-cutting is both labour intensive and a significant HSE risk. In summer, the region is very boggy and the movement of vehicles causes deep ruts and restricts movement. The use of helicopters allowed Integra to reduce the amount of tree-cutting and limit the use of vehicles thus reducing the impact on the environment.

In the Uvat region helicopters were used to move geophysical ground equipment and demonstrated nearly a 2 fold increase in productivity measured by the average number of shot points acquired per day with a daily maximum of over 700sps/ day. The increased costs of helicopter operations can be offset by increased efficiency and reductions in vehicles and personnel. Future operations could be extended to include movement of drilling equipment as well as seismic recording equipment.

Mulchers
Over the last few years the biggest contributor to seismic industry fatalities and injuries was tree-cutting. The industry cuts a significant volume of trees every year, approximately 300,000 line kilometers, and tree-cutters are exposed to significant HSE risks due to falling trees and debris. The efficiency of seismic operations is also dependent on the quality of line preparation. Typically tree cutting operations are carried out in summer to ensure residual tree stumps are cut to a minimum - stumps visible above winter snow cover often limit the movement of drilling equipment. The disposal of cut trees and debris is both time consuming and a requirement to allow the safe passage of vehicles. This adds to the time and risk of manual tree-cutting operations.



In 2007, Integra purchased a mulcher to test the efficiency and suitability of equipment regularly used in other areas of the world for tree-cutting. The equipment was deployed on the same summer project as the heli-portable operations in the Uvat region. The advantage of mulchers is that the number of people involved in tree-cutting operations is reduced from a typical 5 man manual tree-cutting crew to a single operator who is totally enclosed in a safe cabin. The machine effectively "pushes-over" trees and a series of teeth, on a rotating drum, chop the fallen trees in to a fine mulch of wood chips that are deposited behind the machine.



The deployment of mulchers has demonstrated a significant reduction in HSE incidents on tree felling operations with no incidents to date. The effectiveness of mulcher operations has also been proven with a single mulcher capable of clearing between 4-5 kms/day compared with a typical 1km average for a tree-cutting brigade. The advantage of the debris left after mulcher operations is that it provides a flat surface through the cut line that allows a safe and efficient "road-way" for drilling and seismic recording vehicles to follow. A further advantage of a better roadway is that there is less stress on cross-country vehicles and therefore reduced equipment failure and maintenance.

Average operational costs for mulchers and manual teams are comparable but reduced camp sizes and lower HSE risks demonstrate the benefits of such technology. The down-turn in North American seismic market means operators in Canada and the USA are now able to offer high quality machines suitable for the Russian terrain and climatic conditions. Now many leading seismic operators are now looking to stimulate the Russian contracting industry to provide a significant volume of mulchers for the 2009-10 winter season.

High productivity vibroseis acquisition
Approximately 50% of Integra's projects use vibroseis seismic sources. These are commonly used on the flat terrains of the Russian tundra and Kazakhstan Steppe. Individual vibroseis shot points typically use 4 vibrators simultaneously vibrating for up to 20 seconds, known in the industry as a sweep. Oil companies normally request up to 4 or 6 sweeps per shot point. Average survey acquisition rates for Integra operations are between 250 - 300 shot points per day. Daily productivity can be as high as 400 - 500 sps / day depending on weather conditions and terrain. Standard 3D seismic surveys require the acquisition of 20 - 25,000 shot points which will generally take 3-4 months to acquire - the normal duration of the Russian winter season.



Globally, acquisition companies have started to deploy multiple fleets of vibrators and significant volumes of ground equipment to increase vibroseis productivity. This means oil companies are able to acquire larger surveys or high data density coverage during a single operating season. In 2009 Azimut Energy Services has been contracted by a consortium of oil companies to conduct a 3D seismic survey requiring over 250,000 shot points in a area of complex field infrastructure. At typical acquisition rates this would normally take over 2 years to acquire but the consortium's requirement was to acquire the entire data set in 2009.

Working closely with the operator, Azimut was able to design a survey that could be completed within 9 months. The requirement was to utilize up to 10 vibrators, 18,000 channels and 19,000 geophone groups. With it's combined Russian and Kazakhstan resources the company was able to offer the consortium top quality HVA-IV ION vibrators and Sercel 428 ground equipment. The survey design called for 4 groups of 2 vibrators working in both flip-flop and slip-sweep acquisition mode acquiring a single sweep at each shot point. The chosen deployment of the vibrator groups allowed simultaneous operations with some groups vibrating and acquiring data whilst others travelled to a subsequent shot point. 18,000 channels were deployed in the field with an active spread of 9,900 channels. The 428 central electronic system was upgraded to handle the large active spread and new communication equipment acquired to allow the central electronics to "manage" the vibrators and distribution of the channels in the active spread.

The current operations are impressive and have almost certainly set a record for daily production in Russia and Kazakhstan. To date over 100,000 shot points have been acquired in just over 2 months with an average daily productivity of -1700 sps / day. The highest productivity achieved to date was just under 2900 sps / day, the equivalent of 6 seismic parties under normal conditions.

The handling of such daily volumes and advanced electronics has not been without its challenges but the experience gained on this survey will allow Integra to offer advanced acquisition technology to oil companies in Russia and Kazakhstan and allow it to compete globally with western seismic acquisition companies.

Labels: 2D 3D seismic survey, Exploration, onshore acquisition, Russia oil gas

posted by The Rogtec Team @ 16:03  0 Comments