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Il dialogo sull’origine delle montagne di Valerius Faventies (De montium origine, 1561)
No full textIl De montium origine è un breve dialogo che tratta il tema dell’origine delle montagne. Scritto in lingua latina da Valerius Faventies, autore di cui poco sappiamo, fu pubblicato a Venezia nel 1561, sotto gli auspici dell’Accademia Veneta. Esso raccoglie minuziosamente tutte le teorie note agli studiosi del tempo riguardo alla nascita ed alla possibile evoluzione nella storia delle terre emerse. Da erudito, Faventies rielabora e riassume tutte le teorie e le ipotesi sull’origine delle montagne attraverso le fonti dei classici greci, latini e medievali.
L’approccio di Faventies al problema dell’origine delle montagne non è tuttavia quello di un grande innovatore, almeno sul piano dell’apporto di contributi concettuali originali: le nuove concezioni sulla speculazione geologica che costituiscono il primo decisivo strappo nell’ormai infeltrito tessuto del pensiero cinque-seicentesco saranno esposte solo nell’opera di Nicolò Stenone, nota come Prodromus (1669).
Faventies non riesce a fare i collegamenti tra le varie teorie che espone, né riesce a trarre qualche conclusione che possa essere di spunto per una verifica sul campo; egli non è né un osservatore, né uno sperimentatore. Nulla è accennato, compreso o dedotto tramite la possibilità dell’osservazione diretta della natura. Georgius Agricola, che aveva già fatto scuola in fatto di osservazione diretta e non speculativa, rimane lettera morta. Faventies sembra non conoscere la sua opera, o volutamente non la cita, anche se riprende a larghe mani le descrizioni sulle cause dell’origine delle montagne riportate da Agricola nel De ortu et causis subterraneorum. Fortunatamente però, Faventies riesce a raccogliere tutte le conoscenze derivate dalla tradizione con buon ordine, unitamente ad una non comune chiarezza espositiva
The birth of petroleum geosciences in Italy
No full textThis paper investigates the achievements of petroleum geosciences that developed in Italy between the mid-19th and early 20th century, paving the way for the birth of the national oil industry and the establishment of a common cultural and technical milieu that attracted to Italy a number of investments and entrepreneurs. The oilfield sector benefited from the contribution not only of academic studies, but also by the input of outstanding geologists and engineers from the Corps of Mines and, last but not least, from the expertise of many field operators. In an attempt to examine the scientific debate of the time, herein are highlighted the crucial issues of interest with regard to petroleum geosciences and the related tectonic studies
Environmental management of land subsidence: Compaction evaluation through radioactive marker technique
No full textSubsidence is a key issue in managing the production of underground fluids, especially in environmentally sensitive areas. This is the case of the Italian Adriatic offshore in front of the historical city of Venice, where several gas fields have been recently discovered. Here, the alleged risks connected with possible land subsidence and coastal impairment are crucial for releasing the authorizations to start a development project. In order to probe such risks, it has been utilized the Radioactive Marker Technique (RMT), nowadays a quite developed method to measure reservoir rock compaction of deep formations, by which it is possible to estimate the uniaxial compressibility coefficients (C m). As it is well known, C m is the chief geomechanical parameter influencing compaction phenomena, and thus its evaluation is vital for subsidence predictions by means of mathematical modeling. Generally, C m can be evaluated by both in-situ and laboratory measurements. Recent field applications seems to confirm that RMT-derivcd C m's match with sufficient precision with the ones calculated from the surface subsidence observed over the field by means of surveys (levelling, GPS, SAR), but are not always in good agreement with laboratory measurements. The present study reports some field applications of RMT in the Italian Adriatic offshore, which confirm that C m's from laboratory measurements are overestimated with respect to the ones obtained by RMT
Static and dynamic reservoir rock compressibility at high pressure
No full textThe paper reports measurements of rock compressibility performed by means of an equipment capable to operate up to 150 MPa confining pressure. Measurements have been performed on 32 samples from 3 sandstone and 3 carbonatic reservoirs. The experimental apparatus was designed to perform both static investigations (deformation tests, to calculate bulk and pore compressibilities) and dynamic investigations (acoustic tests, for the evaluation of undrained compressibility). Results show that compressibility is not constant, but is a function of reservoir pressure. In particular, compressibility of sandstones follows an exponential trend, decreasing rapidly in the first part of the loading cycle, and remaining almost constant at high pressure. Compressibility of carbonatic samples shows the same behaviour, but increases for stresses close to the yield point. The attempt to correlate dynamic and static tests reveals the necessity of additional investigations; in fact, it has been noticed that undrained compressibility measured by dynamic tests yields inconsistent results for non-elastic rocks, and, generally, dynamic measurements do not correspond to the static ones
Acque nella città. Bologna nella storia europea
No full textSin dai tempi antichi, la presenza di corsi d’acqua ramificati all’interno delle città europee di pianura non è sempre dovuta alla geografia di un fiume principale, talvolta d’importanza regionale, presso le cui sponde avevano preso avvio il nucleo produttivo ed abitativo originario della città stessa. Molto spesso i motivi sono diversi, e vanno visti dal punto di vista dell’asservimento della risorsa idrica, alla sua fruizione ed al suo controllo, in termini moderni alla sua ingegneria: per timore della furia della natura le città sono edificate in prossimità, ma arretrate, rispetto ai fiumi e ai torrenti, posizione che garantisce i vantaggi della navigazione sulla quale si basa gran parte del commercio e ripara dalle alluvioni.
Le città europee mantengono o potenziano l’utilizzo diversificato dell’idraulica urbana: “acqua trasporto”, che garantisce l’insediamento di magazzini intorno ai quali si formeranno nuclei urbani; “acqua difensiva”, che protegge dagli attacchi nemici, ordinata secondo un fossato di circonvallazione oggi scomparso o integrato nel centro antico; “acqua chimica”, dalle qualità intrinseche che lava o ammorbidisce le stoffe, o arricchiscono di riflessi le tinture, costituendo così la ricchezza della città; “acqua energetica”, che con la propria forza macina i cereali, folla il panno di lana, ammorbidisce il cuoio, aziona le pompe e, recentemente, produce elettricità di cui la città è prima consumatrice; “acqua alimentare”, che offre la propria purezza e le proprie risorse ittiche. Infine, gran valore di igiene, perché tutte le civiltà usano il potere purificatore e terapeutico delle acque; l’acqua libera il corpo della città di gran parte dei suoi rifiuti
DRILL BITS FOR HORIZONTAL WELLS
No full textThis paper underlines the importance of the correct drill bit application in horizontal wells. Afler the analysis of the peculiarities of horizontal wells and drainholes drilling techniques, advantages and disadvantages of the application of both roller cone and fixed cutters drill bits have been discussed. Also, a review of the potential specific featuries useful for a correct drill bit selection in horizontal small diameter holes has been highlighted. Drill bits for these special applications, whose importance is quickly increasing nowadays, should be characterised by a design capable to deliver a good penetration rate low WOB, and, at the same time, be able to withstand high RPM without premature cutting structure failure and undergauge. Formation properties will also determine the cutting structure type and the eventual specific features for additional gauge and shoulder protection
Measuring reservoir compaction through radioactive marker technique
No full textRadioactive Marker Technique (RMT), an in-situ method to measure reservoir rock compaction and to evaluate uniaxial compressibility coefficients (Cm), is examined here. Recent field applications seems to confirm that RMT-derived Cm's match with sufficient precision with those calculated from land subsidence observed over the field by means of geodetic surveys, but are not always in good agreement with those derived from lab measurements. In particular, here is reported an application of RMT in the Italian Adriatic offshore, which highlights the discrepancies of Cm's measurements from lab and RMT. At present, these discrepancies aren't thoroughly understood, so, from an applicative standpoint, it is still necessary to perform a critical comparison and integration between both set of data
Sull’impiego di alcune pompe idrauliche nel XVI secolo
No full textL'abilità idraulica degli antichi, per certi versi geniale nella captazione, nel trasporto e nella distribuzione, si era sempre arrestata di fronte al problema del sollevamento di grandi volumi d'acqua. L'esigua potenza delle macchine a disposizione fino a tutto il XV secolo aveva condizionato anche lo sviluppo del settore minerario, ponendo seri limiti alla coltivazione di numerosi giacimenti. In mancanza di macchine adeguate per l’eduzione delle acque di miniera, il limite allo sviluppo delle coltivazioni in sotterraneo era legato alla presenza ed alla quota topografica della superficie di livello della falda freatica: le rudimentali pompe già note in epoca classica ed impiegate fino all'alto medioevo, potevano fronteggiare solo la venuta di modeste infiltrazioni d'acqua, essendo limitate sia nella potenza, sia nella prevalenza.
Anche i Codici minerari antichi, riconoscendo il potenziale limite allo sviluppo in profondità delle coltivazioni, stabiliscono precise norme per l'abbandono dei lavori in sotterraneo (resignatio), al fine di scongiurare il possibile allagamento delle miniere confinanti. Nel XVI secolo, l’aumento della richiesta di materie prime e l'esaurimento dei giacimenti più superficiali impose l'estensione delle coltivazioni in profondità; in quelle aree minerarie dove era indispensabile controllare in permanenza le acque d'infiltrazione che invadevano le gallerie, la tecnologia delle pompe vide un notevole sviluppo, soprattutto quando divenne necessario estendere le coltivazioni sotto la falda acquifera
Radioactive Marker Technique Applications to Evaluate Compaction in Environmentally Sensitive Areas
No full textRadioactive Marker Technique (RMT) is a systems to evaluate layer compaction and land subsidence due to underground fluid production, based on the periodic monitoring of the distance between markers inserted into the formation, or onto casing. RMT is designed for the in situ measurement of the uniaxial compressibility coefficient (Cm) of layers under depletion, which is crucial to implement mathematical models to forecast compaction and its effects on the earth surface. After a brief description of measurement principles, the paper describes some aspects of RMT interpretation. A review of the main features of modern tools is given, weak points of measurement procedures and interpretation techniques are underlined and statistical methods utilized to reduce errors of Cm computation are presented. The paper addresses also a new subject of discussion, i.e., the effect of casing on the deformation of the surrounding layers, that are to be quantified in order to obtain more realistic measurements. Researches in this direction must be carried out, in the attempt to clarify some still vague aspects of interpretation techniques, and to assure reliable measurements and clear criteria of RMT applications. In general, RMT-derived Cm's match with sufficient precision with the ones derived from surface subsidence observed at surface, but not with the ones measured in laboratory. Finally, an application in Northern Adriatic Sea is presented, where RMT helped to improve the quality of lab-measured Cm's, allowing for a more precise environmental impact assessment of a possible hydrocarbon development project in a very sensitive area. At last, the well-studied case of Groningen gas field, and other offshore North Sea and Gulf of Mexico applications are reported
Rock-bit wear in ultra-hot holes
No full textThe paper presents a new model of rock-bit wear, and refers to bits utilized in ultra-hot wells drilled in the geothermal area of Larderello, Tuscany, Italy. In particular, the model, conceived from field data, indicates that the correct evaluation of rock-bit wear, considered in the light of the knowledge of drilling parameters and downhole conditions, can improve the overall drilling performances through a better interpretation of the relationships among rock-bit, formation properties and bottomhole temperature. This paper investigates the detrimental effects, not yet very well understood, of high bottom hole temperature on sealing and reservoir systems of friction bearing rock-bits. A particular bearing wear model for friction bearing rock-bits utilized in ultra-hot holes has been considered and further verified via laboratory inspections on dull bits. A novel interpretation of fiat worn cutting structure has been derived from the above wear model and viable recommendations for improving the cost of drilled interval are suggested. Also, rock-bit field data from several Italian geothermal wells are reported and analized as an example of field application
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