Characterization of drilling mud fluid invasion

SPE Reservoir Evaluation & Engineering, 2004

Geophysics, 2009

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Journal of Petroleum Science and Engineering, 1994

An improved model for prediction ofdrdhng fired filtrate concentration in the near wellbore region is developed and solved numerxcally. 0920-4105/94/$07.00

4th international conference on recent innovations in chemistry & chemical engineering,Iran,Tehran, At Tehran, 2017

Usually in an under-balanced drilling operation, due to pressure difference between mud and formation, amount of drilling mud enters the porous media or high permeable formation and reduces permeability around well bore which is a kind of formation damage. This phenomenon is called drilling mud filtration. In some cases, extreme mud filtration may cause lose circulation which is a dramatic damage. Filtration controlling and keeping it in optimized situation to avoid lose circulation is required to have a successful drilling process. In this research, fundamental concepts of filtration, affecting factors on filtration, methods and relation for measuring filtration and its simulation is discussed.

Muds of different compositions are used in the drilling well process, to support the wall of the borehole along with maintenance of pressure, and to remove rock cuttings generated from the geological formations encountered by the drill bit. The drilling mud invades the formations and modifies the zones surrounding the borehole, mainly, in terms of the physical properties of the rocks, such as porosity and permeability. The identification of this formation damage is important for reservoir characterization, and the subsequent well completion, as well as for the analysis of economic viability. Many years ago, Schlumberger developed a method for determining mud invasion diameter using the Tornado Chart. Today, practitioners in the oil industry use the Tornado Chart to present geophysical logs. Improving upon Schlumberger’s methodology, Crain used mathematical equations to calculate the mud invasion diameter. In this study, we propose a polynomial mathematical method to determine mud invasion diameter. Our method utilizes the same resistivity well logs, namely dual induction log and dual laterology, though different from that of Schlumberger or Crain methods. The approach developed in this study considers the characteristics of the invasion process while quickly and accurately showing results in the form of a log that can be visualized adjacent to other logs measured in the borehole.

1999

A combination of novel petro-physical methods has been used for an integrated investigation of the saturation conditions and characteristics of saturating fluids near the well-bore in sandstone reservoirs. The applied methods include Magnetic Resonance Imaging (MRI), Magnetic Resonance Relaxometry (NMR), Ultra-centrifuge and Gas Chromatography (GC) in combination with Mass-Spectrometry. Routine petro-physical analysis has also been done. The recovered results were used as a basis for the investigation of different objectives. One such objective was the demonstration of NMR logging tool applicability for the study of the invasion. The following subjects were investigated: • Similarities and differences of NMR instrument results from imaging and relaxometry. • The three dimensional porous structure of the core samples. • The effective porosity determination by the NMR method and the evaluation of different models for permeability estimation under invaded zone conditions. • The informa...

SEG Technical Program Expanded Abstracts 2004, 2004

Geophysical Journal International, 2013

To our knowledge, this study is the first to perform a numerical simulation and analysis of the dynamic behaviour of drilling mud invasion into oceanic gas-hydrate-bearing sediment (GHBS) and to consider the effects of such an invasion on borehole stability and the reliability of well logging. As a case study, the simulation background sets up the conditions of mud temperature over hydrate equilibrium temperature and overbalanced drilling, considering the first Chinese expedition to drill gas hydrate (GMGS-1). The results show that dissociating gas may form secondary hydrates in the sediment around borehole by the combined effects of increased pore pressure (caused by mud invasion and flow resistance), endothermic cooling that accompanies hydrate dissociation compounded by the Joule-Thompson effect and the lagged effect of heat transfer in sediments. The secondary hydrate ring around the borehole may be more highly saturated than the in situ sediment. Mud invasion in GHBS is a dynamic process of thermal, fluid (mud invasion), chemical (hydrate dissociation and reformation) and mechanical couplings. All of these factors interact and influence the pore pressure, flow ability, saturation of fluid and hydrates, mechanical parameters and electrical properties of sediments around the borehole, thereby having a strong effect on borehole stability and the results of well logging. The effect is particularly clear in the borehole SH7 of GMGS-1 project. The borehole collapse and resistivity distortion were observed during practical drilling and wireline logging operations in borehole SH7 of the GMGS-1.mud density (i.e. the corresponding borehole pressure), temperature and salinity have a marked influence on the dynamics of mud invasion and on hydrate stability. Therefore, perhaps well-logging distortion caused by mud invasion, hydrate dissociation and reformation should be considered for identifying and evaluating gas hydrate reservoirs. And some suitable drilling measurements need to be adopted to reduce the risk of well-logging distortion and borehole instability.

This report concerns the analysis of the basic techniques of formulating, testing and studying the properties of drilling fluid in contamination with different material encountered during drilling process. This report consists of six chapters with four experiments for measuring the physical properties of drilling fluid such as mud weight (density), rheology (viscosity, gel strength, yield point) sand content, wall building and filtration characteristics. The first chapter consists of introduction and theoretical principals of the experiment. The first experiment was about measurement of mud properties (viscosity density and pH). The second experiment was on mud properties test particularly control of mud weight. This is divided into two parts, Part A was about effect of adding bentonite on mud properties for fresh and salt water base mud and part B was about the effect of adding weight material (barite). It was observed that the viscosity and mud weight increases on the addition of salt to the fresh water mud. Also the addition of barite to the mud affects only mud weight but not viscosity because barite doesn’t have flocculating or deflocculating properties The third experiment was about drilling fluid contamination test. In this test we were studying the effect of contamination of monovalent chemicals (NaCl and KCl) and divalent chemicals that cause contamination are calcium sulfate (CaSO4), cement (Ca(OH)2, and Gypsum (CaSO4-2H2O). It was observed that Sodium chloride increases density of the drilling mud as well as the viscosity of mud since it is flocculant. Cement has a tendency of absorbing water from the mud and increase viscosity, but cement seems to have no any impact on mud weight. Experiment 4 was on determination of sand content of the drilling mud. This is a simple test designed to measure the level of particles in the mud of greater that 200 mesh or 75 microns. From the results obtained in this test and the general field experience shows that the sand content must not be permitted to rise above 2%, otherwise wear on pumps and tubulars will be the result. Any increase in sand content must be investigated since it is often an indication of poor solids removal efficiency.

Drilling is an important part of the oil industry and penetration rate must be enhanced to ensure speedy completion of drilling operation. Weight on bit, Rotary speed, drill bit type, formation characteristics and mud properties are the basic factors that affect the penetration rate of a bit. The focus of this work is on density which is a rheological property of the drilling fluid. Data obtained from eight wells were analyzed to ascertain the effects of Mud density on penetration rate. Water and Oil based Muds were used to drill these wells which were in Sandstone/Shale formations and Penetration rates were plotted against the mud weight. From a field in Alaska, another set of data were obtained to illustrate the effect of Plastic viscosity and Methylene Blue Test (MBT) on the penetration rate. For the Water based mud, the average densities of 10.5, 11.5 and 8.9 ppg. produced average penetration rates of 25 and 24 and 37 ft/hr. respectively. Similarly, the average penetration rates of 28, 35 and 50ft/hr. were obtained by the Oil based mud densities of 11.3, 11.1 and 8.6 ppg. respectively. It can be deduced that the rate of penetration was reduced by the increase in Mud density. In order to drill effectively and efficiently, the right drilling mud density should be formulated. A substantial amount of time and drilling cost can be saved in drilling cost analysis when drilling conditions are suitable to facilitate fast penetration rates and good hydrostatic pressures.