Gazprom Neft Orenburg First performs first multiple hydraulic fracturing in carbonate reservoirs
Gazprom Neft Orenburg First performs first multiple hydraulic fracturing in carbonate reservoirs
27 September 2013Amultiple hydraulic fracturing operation has been performed for the first time onahorizontal well drilled into carbonate reservoirs* inthe East area ofOrenburg oil and gas condensate field, operated byGazprom Neft Orenburg, asubsidiary ofGazprom Neft. The operation was performed aspart ofGazprom Nefts tight reserves program.
The drilling ofhorizontal wells using multiple hydraulic fracturing isthe key technology for development oftight reserves. This technology makes itpossible tocomplete several hydraulic fracturing operations onthe borehole ofanindividual well inorder toincrease oil recovery byimpacting individual strata one atatime.
Acid multiple hydraulic fracturing involves metered injections ofaspecial gelatinous compound and inhibited hydrochloric acid into the stratum. During the first stage, aviscous layer fills the cracks inthe reservoir. Subsequent acid processing makes itpossible toaccomplish deeper penetration ofthe compound into the stratum. The treated channels remain open, which allows for the cracks tohave ahigh throughput and increases the influx ofoil into the well.
Hydraulic fracturing inthe East area ofOrenburg oil and gas condensate field consisted offive stages. The length ofthe horizontal section reaches 600meters. Atotal oftwo hydraulic fracturing operations were performed ontwo separate production wells. After completion ofthe operations, the combined average flow rate ofboth wells will add uptoapproximately eighty tons ofoil per day. The wells are functioning via natural flow.
The method we’re using toraise oil recovery helps increase the flow rate ofhorizontal wells significantly bybringing larger quantities ofreserves into development. The results weachieved clearly demonstrate that wecan successfully apply acid multiple hydraulic fracturing atnew wells toenhance the development ofthe East area ofOrenburg oil and gas condensate field, says Gazprom Neft Orenburg CEO Alexei Ovechkin.
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The East area ofOrenburg oil and gas condensate field isaunique and one ofthe largest fields inthe Orenburg region. Development ofthe field iscomplicated primarily byits geological characteristics, since fractured carbonate reservoirs with ahigh gas/oil ratio and hydrogen sulfide content predominate atthe field.
* Reservoirs are rocks that contain empty spaces within, are permeable, and inwhich water, oil, and gas can move under the effect ofgravity and anoverburden pressure differential. Terrigenous reservoirs are composed ofsand, siltstone, sandstone, siltite, certain types ofargillaceous rock. Fifty-eight percent ofthe world’s discovered oil reserves and 77percent ofgas reserves are associated with reservoirs ofthis type. There are only two main rock-forming minerals incarbonate reservoirs: calcite and dolomite. Oil and gas filter through them primarily via cracks and caverns. Carbonate reservoirs, unlike terrigenous reservoirs, can besubstantially improved interms oftheir filtration properties and storage capacity bymeans ofartificial treatment with solutions ofhydrochloric acid and carbonated water, aswell asthrough other methods that take advantage ofthe chemical reactivity ofthe calcite and dolomite.
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