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Depleted gas reservoir management improvement by implementing specialized mobile teams

Lupu D.-A., Foidas I., Sutoiu F.

AGH Drilling, Oil, Gas

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2018

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Vol. 35, no. 1

271--282

EN

The state of depletion of gas reservoirs generates many challenges for production management teams that focus their efforts to operate the fields in a rational and efficient manner in order to achieve attractive recovery factors. An essential activity in terms of production management is related to the maintenance programs, particularly in the current paper, on those exploitation perimeters extended as a surfaces. This aspect, directly influences the maintenance activity in daily basis on the gas wells such us soaping and flowback programs for liquid unloading, visual inspection of wellhead integrity and pressure measurements. It has been noticed throughout the production history that the wells located on extended exploitation perimeters as surfaces, some of them being placed in isolated areas, have low productivity and do not produce at their potential. The causes identified in this regard are as follows: – The wells are liquid flooded or loaded and are not able to unload using their own energy being in an advanced stage of depletion. – There are not enough representative production data recorded to monitor the real performance and intervene in the right time, in order to improve the well productivity. The relatively large distances between the wells and the technological groups correlated with difficult access to the well location are the main arguments for the implementation of the specialized mobile teams which aims to monitor the wells performance, to ensure a safe exploitation process of the productive infrastructure, to improve the field management activity, respectively to increase the wells productivity.

2

Productivity stimulation of depleted reservoirs by applying new technologies to open the productive layers

Vlasin I., Stefanescu D.-P., Sutoiu F.

AGH Drilling, Oil, Gas

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2017

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Vol. 34, no. 2

569--576

EN

The greatest natural gas fields belonging to Romgaz company are characterized by an advanced stage of exploitation, which actually involves a special approach, from the perspective of the works performed in the wells. As part of the most recently Romgaz strategy, for these fields have been created new geological models based on 3D seismic acquisitions, which allowed identifying some new less drained or even undrained zones. This aspect created the premises for developing the opportunities for capitalization of the new reserves volumes, by applying the advanced technologies of opening productive layers by perforation and reperforation operations with deep penetration guns, using also underbalance conditions. We mention also that new cased hole geophysical methods like PNN and RCI consisted also important elements in establishing the perforation intervals and identifying the by-passed layers. The paper contains some relevant case studies, which illustrates the efficiency of these new methods.

3

Operations for improving the gas flow in the wellbore adjacent zone

Sutoiu F., Foidas I., Avramescu M.

AGH Drilling, Oil, Gas

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2016

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Vol. 33, no. 2

531--547

EN

During the whole period of a natural gas reservoir exploitation, from the start of production until the total reservoir energy depletion, may apear some phenomena which by their nature can affect the natural gas flow from the layer into the well. The flow resistance greeted by gas in the adjacent borehole may have multiple causes. In the majority of cases, geological elements are those which definitive influence the behaviour in exploitation of those reservoirs, so the existence of some traps due to the continuity and discontinuity character of the porous-permeable medium or to some reservoir parameters with low values, drasticaly reduces the posibility of extraction of a bigger volume of geological gas resource. Also the exploitation performances of gas reservoirs, through different wells, are major affected because of the skin factor. This produces an increased flow resistance in the adjacent zone of the borehole which is a plus to the resistance caused by the hydrodynamic imperfection to the mode and open degree of the productive layer. During the maturity stage of natural gas reservoirs, a special attention is granted to prevention and control of this unwanted effects which may affect natural gas flow from the reservoir into the well, through different operations. The stimulation of these productive layers through different operations aiming the reduction of geological nature constraints, thereby become a complex approach having the finality the increasing of exploitation performances itself. In Romgaz were tested and are used a series of stimulation technologies of the productive layers. From there historic we conclude that perforations or re-perforations using deep penetration tools, acidizing and nitrogen injection are applied with success to the productive wells. Regarding the increasing of the recovery factor for wells with high water income or for wells with mixed flow regime or with water drive regime, were successfully tested the polymer injection technology that helps to maintaining or optimising the productive wells.

4

Mature gas fields rehabilitation concepts

Tataru A., Sutoiu F., Sandor B.

AGH Drilling, Oil, Gas

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2014

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Vol. 31, no. 2

253--261

EN

Rehabilitation operations are applied to mature gas field, which although have a significant history production, owns a continuous energetical capacity which could be exploited in economicaly efficient conditions. For rehabilitation are selected from all the mature fields those which could additionally offer to the currently obtained basis production, a supplementary production, generated through interventions in reservoirs, wells or surface infrastructure. Although the opportunity of mature gas field rehabilitation is evident and unanimously accepted, the effective implementation of the concept represents a complex intervention. This fact is just due to natural gas reservoirs diversity, which involves developing particular models of rehabilitation, adapted to each reservoir capability. Conceptually, mature gas field rehabilitation can be divided in three sequences: reservoir, well, surface facilities. Intervention in one section or another, or concomitent intervention in all three sequences, is dictated by technical and economical reasons. Mature gas field rehabilitation must begin with main production problems identification that once recognized can be solved by remedial actions. Such corrective measures are commonly used in order to inerease the productivity of gas wells and removing restrietions on reservoir - well - surface facilities route.

5

Rigless jobs in gas wells

Sutoiu F., Tataru A., Simescu B.

AGH Drilling, Oil, Gas

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2013

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Vol. 30, no. 1

221--229

EN

At the same time with gas reservoirs energetic depletion there appears the perforation deterioration or blockage issue. Mostly, in the mature gas reservoirs, a big attention must be given to well interventions for maintaining or increasing the production. Because of the workover operation risks and costs, the oil companies prefer as much as possible rigless jobs to accomplish well stimulation like reperforation or several coil tubing operations (acidizing, fracturing etc). In our rehabilitation programs for many gas reservoirs, our company accomplished successfully more stimulation jobs. In this paper, we will present some case studies and results obtained after several rigless operations which assure long term production increases.

6

Changing well completion in a mature gas well using velocity string

Piteiu M. A., Sutoiu F., Simescu B., Costin N.

Wiertnictwo, Nafta, Gaz

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2008

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T. 25, z. 2

595-601

EN

In a gas field production decreases over time and can eventually stop producing completely because of liquid loading. As the reservoir pressure in a gas well depletes, there may be insufficient velocity to transport all liquids from the wellbore. In time, these liquids accumulate and impair production. The factors that are causing this problem include declining reservoir pressure, gas velocities and increased water production. One method of restoring a well that is liquid loaded back to flow production is installing a smaller diameter tubing string to run inside the production tubing of a well. Regarding advanced rate of depletion in Romgaz gas fields, reinjection method gives viable solutions to face the problems that appear in the exploitation of the wells with appreciable liquid impurities production.

PL

Z czasem produkcja na złożu gazowym ulega zmniejszeniu aż do całkowitego jej zaprzestania. Ciśnienie złożowe w otworach gazowych zmniejsza się powodując, że brak będzie siły wynoszącej płyny z otworu na zewnątrz. Z czasem płyny te kumulują się, uniemożliwiając dalszą produkcję. Czynnikami odpowiedzialnymi za te utrudnienia są obniżenie wartości ciśnienia złożowego, zmniejszone prędkości przepływu gazu oraz zwiększona produkcja wody. Jedną z metod stosowanych w przypadku otworów z reiniekcją jako sposobem na wymuszenie produkcji jest zastosowanie rur produkcyjnych o mniejszej średnicy wewnątrz rury wydobywczej. Metoda ta - iniekcji - jest skutecznym rozwiązaniem tego problemu w firmie ROMGAZ.