Aim of the project is efficiency increase of hard rocks destruction at borehole bottom by developing DRILLING MUD solution and evaluation of its influence on DRILLING process. The article presents the results of studies directed on studying of DRILLING MUD composition (the choice of reagent concentrations, taking into account the filtration properties, structural and rheological parameters, study of the temperature effect influence on the quality of the solution). Experiments of metallic indenter penetration into the glass sample at various number of strikes in the water and surfactant solutions are presented in the article. Paper also offers investigation devoted to development of clayless MUD solution with surfactant addings, which will allow increase of hard rocks destruction efficiency. Results of industrial test trials of developed MUD solution are also represented, showing implementation of developed DRILLING MUD composition to increase productivity of DRILLING operations by maintaining high DRILLING speed and advance per bit.

CMC polymer is used as an additive to decrease water loss and MUD-cake-thickness in MUD DRILLING. In this study, the effect of CMC and CMC nanoparticles on water loss and MUD-cake-thickness in MUD DRILLING is investigated. CMC nanoparticles are made by using of ball milling and their size is measured by Particle size analyzer. CMC and CMC nanoparticles which were prepared by Hamilton batch mixer and with certain percent suggested by API, were added to the WATER-BASED MUD DRILLING. The amount of water loss and MUD cake thickness was measured by filter press. It was found that adding CMC nanoparticles in comparison with conventional CMC resulted in desirable reduction of amount of water loss and MUD cake thickness.

Filtration index of the DRILLING fluid is an important parameter of well DRILLING, especially at DRILLING-in the reservoirs. Standard parameter in the study of DRILLING fluids is static filtration index. At the same time, it is more feasible to determine dynamic filtration index, if considering actual conditions of the well. Use of polymer carbonate-weighted DRILLING fluids is advisable at DRILLING-in oil and gas formations; but, it is also necessary to take into account fractional composition of the weighting agent. Aim of the work is to study the influence of weighting-bridging agent's fractional composition on DRILLING fluid's dynamic filtration index. Taking into account main theories of bridging agent selection, such as the theory of Abrams, Kaeuffer and Vickers, will make it possible to define the influence of carbonates “ blend” on the filtration losses of the DRILLING fluid. Dynamic high pressure high temperature (HPHT) filter was used in this research, which allows measuring filtration properties of the DRILLING fluid as in standard HTHP test, with fluid circulating inside the cell. In order to get results that are closer to real conditions, in addition to the standard paper filter, studies were carried out on ceramic disks with a known porosity. Theories on selection of bridging agents considered in the paper have their advantages and disadvantages. Depending on available data on the reservoir (for example, data availability on porosity and permeability) and access to high-quality bridging material, a more effective theory is chosen and the negative effect of the DRILLING fluid on the productivity of the formation is reduced.

The objective of this study was to investigate the rheological behaviour of DRILLING fluid prepared by mixing DRISP AC LOT#1104 polymer with water base MUD at different concentrations. The effect of polymer addition on the two rheological models, namely power law and Bingham plastic was also investigated. The addition of polymer enhances the plastic viscosity, apparent viscosity, yield point, and the gel strength of the studied polymer MUDs. In addition, this polymer induces the pseudoplastic property model, while the power law model works better for two different ranges of shear rates.

An improved model of MUD dispersion has been introduced in this work. The advantages of this model consist of a new analytical correlation for dispersivity by using resistivity log data and using a new aspect of capacitance dispersion model. Mathematical formulations were expressed, solved by numerical model taking advantage of actual log and formation data. Achieved results yielded reasonable values and trends which can be used to predict the DRILLING fluid concentration near wellbore region and interpret the well log data. In comparison with the previous models (Civan and Engler, 1994; Donaldson and Chernoglazov, 1987), this model uses more reasonable data and assumptions making it closer to real conditions.

DRILLING cost optimization has always been an important issue in the petroleum industry. In order to save costs and create new markets for local materials, Detarium microcarpum also known as ofor and food gum (Cissus populnea) powders were evaluated in this study at high temperature as an alternative to imported chemical additives in WATER-BASED DRILLING fluid. The base MUD composed of alkali beneficiated local clay, Brachystegia eurycoma also known as achi, corn and cocoanut fibers whose viscosity, yield point and gel strength fell short the recommended API standard from preliminary analysis. The two factors were combined using experimental design technique and MUD properties optimized numerically using desirability function. At optimum conditions, The MUD’s properties are as following: Plastic viscosity, PV (18.4±0.63 cp), Yield point, Yp (15.7±0.9 lbf/100ft2), Fluid loss (FL) (12.1±0.37 ml) and 10 min Gel strength (5.6±0.05 lbf/100ft2). These values are in good agreement with the API recommended standard. Both biopolymers exhibited high potential at low and moderate temperatures. However, food gum is thermally stable, a good rheology stabilizer and filtrate reducer up to the test temperature of 185oF. The presence and nature of salts in solution influences differently the viscosity of the two biopolymers.

DRISPAC Polymers are one of the most effective groups of additives which are being used to depreclate the water loss dulling MUDs.In this work performance of the MUD-free-polymer is verified at various concentrations. Furthermore, the effect of polymer DRISP AC on water loss behavior at a WATER-BASED MUD (Bentonite) is investigated at various concentrations.The results show that the polymer may be considered as an effective additive, and its effect on modification of the MUD behavior may be more considerable with respect to the Bentonite. In addition, at high concentration the effect of the polymer is reduced.

DRILLING fluid is the most important lifeline of the DRILLING operation, that main task is facilitate the cuttings removal of the DRILLING. There are varieties of DRILLING fluids such as sodium bentonite based-DRILLING fluid is called “MUD” and DRILLING foam or surfactant based-DRILLING fluid is called “soap”. The present work aims are study on the modified DRILLING MUD properties by using the TiO2/ Polyacrylamide (PAM) as a nanocomposite additive. This additive was obtained through the aqueous solution polymerization of acrylamide monomer in the presence of TiO2 nanoparticles and high hydrophilic-lipophilic balance (HLB) surfactants such as sodium dodecyl sulfate (SDS) and polyoxyethylene sorbitan mono-oleate (Tween 80). At first, the TiO2/ PAM nanocomposite was characterized by XRD, UV-Vis, FTIR, DLS and SEM. Then the viscosity, density-specific gravity- and filtration properties of the modified DRILLING MUD were investigated in different amount of nanocomposite compounds. The results indicated that the density, fluid loss and filter cake thickness of the modified DRILLING MUD were decreased with the increase of the surfactant concentration, whereas the viscosity was increased. With the increasing amount of SDS from 0.1 to 1.2 g in the synthesis process, the viscosity was increased approximately 4 cP and the density was decreased about 0.1 specific gravity. The nanoparticle and HLB value were affected in the filtration properties, but in general, that improved the fluid loss and filter cake thickness about 28 and 38% compared the based DRILLING MUD, respectively.

Kangan and Dalan formations are one of main reservoir rocks in Fars structural province in Iran south. in XXP gas field available fractures in Kangan formation have main effect on DRILLING MUD loss. Although shale rate change of reservoir rock units is a key factor in control of fractures distribution in upright direction. But lateral distinction in reservoir rock leakage is affected by opening amount of intersection fractures. During 31 wells DRILLING in TBK, DRILLING MUD loss has occurred in 12 wells. DRILLING MUD loss in these wells has been observed in Kangan formation and in anticline axis range. On the basis of surface studies and EMI images’ interpretation, two major groups of fractures with non tectonic origin have been recognized in XXP anticline. These fractures have geometric characteristics including Dr. 150/80, Dr. 240/80. Two desired fracture groups are crossover and vertical on layered surface. These fractures are co-direction and intersection type with main fractures of southern Pars field. Desired fractures have evolved by the effect of upper layers’ weight before folding. Fracture Intersection have been stretched in fold axis range by folding effect and extra opening has been occurred on their surface. Extra opening of fractures intersection in fold axis range has caused DRILLING MUD loss increase in this part of the field.