Wells conditions are different in wide range of temperature and depth. Cement slurries in such conditions have to remain pumpable and after setting to stay homogenous in production well life. For cementing operations in wide range of temperature and pressure and to accommodate cement slurries for individual well requirements more than 50 additives are now used for various API classes of cement. Laboratory in NIS -National oil company of Serbia, provides cement analysis of dry cement, tests on cement slurries and cement stone in compliance with methods prescribed by API standard, whereby quality and type of equipment fully meet the requirements. Adaptation of the local cement to the well conditions had already been done by these additives and by numerous tests of pure cement and cement mixtures we developed a palette of typical cement mixtures for cementing oil wells in the south eastern region of the Pannonian basin.

Cemented boreholes annulus its stability achieved tightness must be maintained in the continuation phase of drilling, is that in the process of drilling, cementing, production. Preserving stability in the working life of the wells threatened and technological stage of the production process due to the natural development of conditioned stress-laden formation (swelling) and a reduction of fluid volume in the reservoir and operational procedures (from moderate to high pressures and temperatures, as well astechnical interventions (changes type of working fluid, leaking testing, perforating, injection, hydraulic fracturing, other operations). From cement mixture composition depend on the mechanical properties of hardened cement stone. Increase elasticity is associated with a reduction in the compressive strength and must always check that the compressive strength of cement stone ensure the stability of pipes due to well working life.

The oil reservoirs of the southeastern part of the Panonian basin are characterized by considerable presence of water,i.e.waterdrive. The hydrocarbon reservoirs are mostly in the middle and final production stages. The water production is especially significant in wells producing with an installed Electrical Submersible Pump (ESP). As production continues, it is a realistic expectation that the water cut increases as well.The rapid production of water has affected fluid production in a significant way.Produced water in the Elemir oilfield is gathered, treated and then injected into the porous layers through several wells.The current system for the preparation and treatment of produced water in the Elemir oilfield has functioned with evident technical issues.The main problems are increased volumes of produced fluids and the deposition of solids (scales) in water treatment system. In thisarticle, a new model for produced water treatment is presented, including technical, economic and environmental aspects. A new model fulfils volumetric requirements, improves oil/water separation and suspended solids removal which lead to better injection performance.

<p>World production of pipes is mainly based on the standards of API. However, this does not obligate you to use exclusively for casing manufactured by API standards. The wells that will exploit the hydrocarbons and aggressive media, install the protective casing made of alloy steel not yet covered by API standards. Running casing operation holds a special place in all phases of the wells because of protective casing account for a high percentage of the cost of drilling and improperly designed pipe string (or damaged by corrosion) increased costs due to repair of the object. If the fluid layer which produce, present aggressive gases (CO2, H2S, Cl), under certain thermodynamic conditions, it may cause significant corrosion of pipe materials. That created openings in the casing string may allow migration of gas. For this reason it is necessary to know the limits specified partial pressures of gases and estimate conditions in which corrosion is expressed.</p>