Inainte de a contesta gazele de sist e cazul sa stim ce sunt acestea si ce riscuri presupune exploatareaBefore Fighting Against Shale Gas, We Should Know What It Is

Resursele conventionale de gaze naturale ale Romaniei ar acoperi consumul actual pe o perioada de 10-15 ani, cu o conditie: investitiile in vechile exploatari sa creasca, ceea ce inevitabil va duce la o majorare a pretului. Plecand de la acest adevar recunoscut in unanimitate, alternativa exploatarii gazelor neconventionale este in momentul de fata singura varianta pe care specialistii din industria gazelor o intrevad, astfel incat importurile sa poata fi mentinute in limite rezonabile, sau chiar eliminate. Cel mai recent Raport al Energy Information Agency (EIA) arata ca gazele neconventionale ar majora cu cu 47% rezervele potentiale de gaze naturale recuperabile la nivel mondial, ceea ce reprezinta 32% din rezervele totale de gaze naturale.

Cum sta Romania in context? Rezervele recucperabile ale tarii noastre sunt estimate la 1.444 miliarde metri cubi, ceea ce ne situeaza pe locul trei in Europa dupa Polonia ( 4.190 miliarde metri cubi) si Franta (2.869 miliarde metri cubi). Polonezii au trecut deja la faza de exploatare, francezii au instituit deocamdata un moratoriu pentru mai multe amanunte, iar Romania nu stie in ce directie s-o apuce. Intr-adevar, problema nu este deloc simpla iar interesele politice, comerciale si de alta natura au o conotatie extrem de puternica in toata aceasta poveste. Tocmai de aceea, Energy-Center va gazdui in cateva analize opiniile specialistilor din Romania, reunite intr-un studiu de mare amploare realizat de Centrul European de Excelenta in domeniul gazelor naturale din argile gazeifere.

Facem precizarea ca la acest studiu au contribuit peste 40 de specialisti romani, care in colaborare cu specialisti din alte 30 de tari au ajuns la concluzia ca gazele naturale neconventionale trebuie exploatate. Desigur, nu in orice conditii.

Ce sunt gazele de sist?

Cu toate ca este un termen mai putin acceptat de catre specialisti (corect este gaze neconventionale), gazele de sist sunt gaze naturale aflate in argile gazeifere, care fac parte din categoria zacamintelor neconventionale de hidrocarburi si au o compozitiechimica identica cu cea a gazelor naturale din zacaminte conventionale, respectiv gazul metan. Pentru ca Romania nu are inca o strategie energetica adaptata contextului international, este important de stiut ca evolutia conceptelor si noile standarde la nivel european privind resursele naturale energetice neconventionale depind de buna cunoastere a potentialului in astfel de resurse, de evaluarea rezervelor si a calitatii lor, de distributia lor in teritoriul vizat si, in final, de modalitatile de valorificare a acestora.

Tocmai asta incercam acum prin lucrarile de explorare. Resursele energetice neconventionale constituie o forma alternativa de energie, ele sunt localizate la adancimi mari in scoarta terestra. Este foarte important de subliniat acest lucru pentru atunci cand ne vom referi la tehnologia de extragere si la riscurile pe care le presupune. In Romania, formatiunile argiloase cu potential gazeifer de tipul gas shales sunt localizate in zonele adanci din Carpatii Orientali, precum si in unitati de platforma (din fata Carpatilor) la adancimi ce depasesc 2.500-3.000 de metri (Platforma Moesica- Campia Romana) , cu extinderea sa in Dobrogea de Sud, Platforma scitica (Depresiunea Barladului), sudul Platformei Moldovenesti. De asemenea sunt indeplinite conditii potentiale de existenta a gazelor in Depresiunea Getica, Depresiunea Panonica si in Bazinul Transilvaniei. Pentru toate aceste locatii exista aprecieri ale specialistilor, fata de potential, asupra carora vom reveni.

Tehnici-tipuri de foraje

Volumul mondial actual de resurse de gaze din formatiuni neconventionale depaseste 32,560 tcf (trilioane de picioare cubice) si nu exista nicio indoiala ca pe masura ce tehnologiile specifice vor progresa aceste estimari vor fi revizuite, cel mai probabil in sens pozitiv. Dintre acestea, 16,112 tcf sunt gaze de sist (shale gas). Specificul acestor zacaminte consta in faptul ca gazele sunt absorbite in matricea argiloasa si se intind pe suprafete relativ mari in planuri aproximativ orizontale. Concret, acest specific impune, in vederea exploatarii lor, o interfata de contact sonda-zacamant foarte mare.

La ora actuala, pentru exploatarea gazelor de sist se folosesc eficient, cel mai adesea, forajele orizontale combinate cu operatia de fisurare hidraulica. Este vorba mai ales de foraje cu actiune extinsa, cu lungimi ale portiunilor orizontale de mii de metri. Sunt consacrate cateva tehnologii de orientare moderne, care pot raspunde acestor probleme. Amintim ca la noi in tara au fost sapate sonde orizontale incepand din anul 1995, cu sonda 1 Clejani. Sonde dirijate si orizontale a realizat cu precadere societatea Foraj Sonde Targu Mures. Astfel, numai in perioada 2008-2012, aceasta intreprindere a realizat un numar de 34 de astfel de sonde.

Evaluarea rezervelor de shale gas trebuie sa se faca dupa proiectarea si forarea unor sonde de explorare care sa stabileasca, printr-o abordare 3D-geometria (arhitectura) corpurilor de roca , grosimea lor, extinderea laterala, omogenitatea litologica, permeabilitatea formatiunii in ansamblul ei. Nu in ultimul rand, trebuie sa continue cercetarile pentru evaluarea rezervelor de tight gas (Depresiunea Panonica si Bazinul Transilvaniei), carbuni gazeiferi (Bazinul Aninei) si a gaz hidratilor din Marea Neagra.

(va urma)Romania’s conventional gas reserves would cover the consumption at present levels for 10-15 years, on one condition: investing more in the old fields; this would inevitably lead to higher prices. Based on this undisputed reality, for the time being the only alternative is the exploitation of unconventional gas, according to the experts of the gas industry; this would keep imports at reasonable levels or would eliminate them altogether. The latest report of the Energy Information Agency (EIA) shows that unconventional gas would add 47% to the potential natural gas reserves worldwide, which is equivalent to 32% of all the reserves of natural gas.

What is Romania’s position in this context? The recoverable reserves of our country are estimated to 1444 billion cubic meters, placing Romania on the third place in Europe, after Poland (4190 billion cubic meters) and France (2869 billion cubic meters). Poland has already started the exploitation, while France set up a moratorium for several details, and Romania is undecided. The problem is indeed very complex, and the political, commercial and other interests involved are very strong. This is why Energy-Center will host, in a series of analyses, the opinion of Romanian experts, gathered in an extensive study of the European Centre for Excellence in Natural Gas from Shale Gas.

Note that more than 40 Romanian experts have contributed to this study, and in collaboration with experts from 30 other countries they concluded that the unconventional gas should be exploited. But of course, not haphazardly.

What Is Shale Gas?

Although this term is less accepted by experts (the correct term being ‘unconventional gas’), the shale gas is natural gas trapped in shale; it is a type of unconventional reserves of hydrocarbons, with a chemical composition identical to the conventional natural gas, i.e. methane. As Romania lacks an energy strategy adapted to the international context, we must mention that the evolution of the concepts and the new European standards for unconventional natural energy sources are based on thorough knowledge of the potential of these resources, of the evaluation of the reserves and of their quality, of their geographical distribution and finally, on the methods of commercial exploitation.

This is precisely the purpose of the current exploration operations. The unconventional energy sources are an alternative form of energy located at great depths inside the Earth’s crust. This is very important for the extraction technology and for the risks it involves. In Romania, the shale shale formations with gas shale potential are located deep under the Eastern Carpathians, and in plateau units (next to the Carpathians) at depths of more than 2500 – 3000 meters (the Moesian Platform – Romanian Plain) with extensions in Southern Dobruja, the Scythian platform (Barlad Depression) and the southern part of the Moldavian Platform. Potential conditions for the existence of gas are also present in the Getic Depression, Pannonian Depression and Transylvanian Basin. The experts have assessed the potential of all these areas; we shall get back to that.

Techniques and Types of Drilling

The known resources of unconventional gas worldwide are more than 32,560 tcf (trillion cubic feet), and this figure will be probably reviewed, most probably upwards, as specific technologies will evolve. Out of this, 16,112 tcf is shale gas. The specific of these deposits is the retention of gas within a shale matrix, and their relatively wide horizontal extension. In practice, this specific requires a very large interface between the well and the deposit for exploitation purposes.

Currently, the shale gas is most often exploited by horizontal drilling combine with hydraulic fracturing (fracking). Most of the drills are wide range, with horizontal section lengths on the order of thousands of meters. Several modern technologies of directing are known to be fit for this. Note that the first horizontal wells were drilled in Romania in 1995, namely well #1 in Clejani. Directional and horizontal wells were drilled especially by the Foraj Sonde company of Targu Mures. Between 2008 and 2012 only, this company drilled 34 wells of this type.

The shale gas reserves must be evaluated after designing and drilling exploratory wells, which must establish through 3D techniques the geometry (the architecture) of the rock beds, their thickness, their horizontal span, their lithologic uniformity, and the permeability of the formation as a whole. It is also important to continue the researches for the evaluation of the deposits of tight gas reserves (in the Pannonian Depression and the Transylvanian Basin), bituminous coal (Anina Basin) and gas hydrate in the Black Sea.

(to be continued)