Hole cleaning of drilled hole section of planned oil or gas well is considered as a major part of optimization of rate of penetration (ROP). ROP significantly depends on hole cleaning of drilled hole section. Hole cleaning can minimize hole problems such as stuck pipe incidents, drilling cuttings accumulation, torque and drag, erratic equivalent circulating density (ECD) in annulus, wellbore instability, tight spot and hole conditions and improves well drilling performance to maximum limit of rate of penetration which depends on rig equipment as well, however, hole cleaning will help to utilize maximum output of those equipment to achieve satisfactory performance. In addition, hole cleaning contributes effectively to optimize rig performance as well. It can optimize running time of casings, cementing and well displacement. Hole cleaning is practical more than theoretical and it requires immediate intervention for ensuring efficient hole cleaning to have optimized performance of rate of penetration. In order to achieve proper hole cleaning efficiency, it must be planned and engineered in well design. A new hole cleaning automated models or indexes were developed to monitor, optimize and alert drilling team to realize and recognize and perform an immediate intervention to optimize or control well drilling and operations performance. Drilling parameters and fluid rheology were collected and studied to come up with efficient hole cleaning models. Collected parameters were compared with other hole cleaning models parameters and rate of penetration to assign strong, qualitative and quantitative relationships that support developed models. The hole cleaning model (or hole cleaning efficiency index) can be automated and provide general idea about hole cleaning efficiency applied in drilled hole section and optimized drilling rate. The developed models were applied in challenging hole sections and showed improvement in well drilling and operations performance. Similarly, it has shown improvement of drilling rate more than 50%.

Drilling operations are considered a major cost in the development phase of oil and gas wells, which places huge emphasis on drilling efficiency as a leading factor in cost reduction and optimization. Nonproductive time (NPT) incidents such as stuck pipes must be minimized by careful planning and close well monitoring to enhance drilling efficiency. One frequent and global cause of stuck pipes is the inefficient removal of formation cuttings from the wellbore while drilling, which is the focus of the developed real-time model. Poor hole cleaning is also a major contributor to other NPTs such as loss of circulation and formation fracturing, which can be induced due to the high equivalent circulating density (ECD) caused by the presence of excess cuttings. Insufficient hole cleaning, if not tackled properly and in a timely manner, can lead to NPT incidents and consequently increases the drilling cost significantly. In addition to NPT reduction, proper hole cleaning can increase the rate of penetration (ROP) and reduce torque and drag. A tool that provides a real-time indication of the hole cleaning efficiency is therefore very valuable to have better control of the hole conditions, especially in critical wells. Such indicators will provide continuous monitoring of the wellbore and will allow immediate intervention for detected abnormalities. There are several indexes that evaluate hole cleaning efficiency while drilling. The index that will be the core of the developed model is the Carrying Capacity Index (CCI), which is defined as the ability of a mud system to circulate the cuttings to the surface. The index is influenced mainly by the drilling fluid properties and flow hydraulics, which are both controllable factors that allow the rig crew to adjust on location to ensure sufficient cleaning of the cuttings. The developed system automatically calculates the CCI in real-time. Thousands of raw values are generated from rig sensors continuously, which makes the calculations nearly impossible for a human to perform. The model is developed to take in the raw data and use it as an input in conjunction with some well details, such as hole size and casing size, to generate the CCI. This system takes us one step closer toward the ultimate goal of having an integrated and fully automated hole cleaning evaluation and intervention tool that does not require any human involvement.

Evaluating physical properties of rock while drilling can improve and optimize drilling operations and save time and cost of the drilling operation. Logging tools, correlations, mini-frac test, micro-frac test, and coring operations are used to have required parameters of physical properties of rock to have a clear image about features of drilled formation. However, most of them are expensive, consumed time, decelerate wells’ deliveries and have impact of error influence. In this paper, physical properties of rock were calculated by using surface drilling parameters and fluid rheological properties to ensure delivery of wells with efficient drilling operations in optimum time and cost. Surface drilling parameters and fluid rheological properties were collected to evaluate rock physical properties. The drilling parameters and mud rheological properties in certain hole sections were analyzed first to determine the effect of rate of penetration (ROP) and cuttings concentration in annulus (CCA) on physical rock properties of rock. Evaluating physical rock properties while drilling from surface drilling parameters and fluid rheology properties will help and enhance the drilling operations, minimize drilling problems and has a major impact on cost optimization. The data selected are from the same hole size, formation type and mud type. The relationship between collected drilling parameters, fluid rheological properties and physical rock properties were then evaluated to determine the relationships of the correlations strengths. This is the first time to evaluate physical rock properties from drilling surface parameters and fluid rheological properties and showed acceptable calculated values. The results of this work include a developed model of rock bulk density that has been validated and compared with sonic and bulk density logs. The model has shown very low absolute error (less than 2%). Other physical properties of rock were determined based on developed bulk density model by using strong correlations that are applicable for same scenario. Evaluation of physical rock properties in the hole sections was tested and helped estimate bulk density, porosity and Ultimate Compressive Strength (UCS).

Low-density water-based drilling fluids formulated with hollow glass spheres (HGS) offer an attractive drilling method. HGS are incompressible lightweight additives with the capability to reduce mud weight down to 41.0 lbm/ft 3 (5.5 lbm/gal). Several pressure ratings of HGS are available, and selecting the appropriate rating is essential to avoid formation damage and lost circulation in near-balance conditions. Failure of the spheres could thus lead to catastrophic results.The objectives of this paper is to evaluate the stability of inhibited water-based drilling fluids formulated with HGS in diverse pH environments, and assess their potential application in Wasia formations in Saudi Arabia. Wasia formation is composed of middle cretaceous clastic rocks with layers of sandstone, shale and occasional limestone. Wasia is an aquifer with a thick unit that crops out in central Najd with a slight eastward dip (Powers et al. 1966). The pressures of Wasia correlate to equivalent mud weights (EMW) of 51-58 lbm/ft 3 . This range of EMW is lower than that of water, and the use of conventional mud systems could introduce several operational difficulties due to the high hydrostatic pressure they create. The implementation of HGS-based lightweight fluids would lower the hydrostatic pressure in the wellbore, thus eliminating or reducing the frequent loss of circulation experienced in Wasia. HGS-based fluids could also provide greater protection of underground water resources, improve rate of penetration (ROP), and reduce or eliminate differential pipe sticking.We conducted comprehensive analysis of HGS performance in various pH environments to assess their stability in drilling fluids. Mud characteristics and rheological properties were examined before hot rolling (BHR) and after hot rolling (AHR) to determine the effects of high pressure and high temperature (HPHT) on the system. The duration at which the samples were exposed to HPHT conditions varied from 1 to 4 days to understand the behavior of the mud over time. In addition, two typical formulations were prepared using HGS and conventional additives to evaluate their properties and compare them to the American Petroleum Institute (API) standards.Hollow glass microspheres were found to be stable in the pH conditions of drilling operations (pH~9), with a maximum density variation of 0.5 lbm/ft 3 . At higher pH levels (pH Ͼ11), the spheres experienced fractional dissolution due to the reaction of the added NaOH with borosilicate glass. In pH ranges lower than 4, the spheres were found to be extremely stable. The inhibited water-based fluids formulated with HGS produced favorable rheology and stable mud characteristics before and after exposure to the actual downhole temperatures of Wasia formation.

Hollow glass spheres (HGS) provide an attractive method to reduce densities of drilling fluids and cement slurries for different objectives. There are several pressure ratings of HGS and selecting and testing the right type for the suitable application is important.The objective of this paper is to evaluate performance and stability of HGS by formulating HGS based fluids in different pH conditions, formulating low density water based drilling fluids with HGS as density reducing additive, and formulating low density cement with HGS as density reducing additiveThe evaluation of the stability of low-density inhibited water-based fluids formulated with HGS in diverse pH environments was for their potential application in Wasia formations in Saudi Arabia. Intensive testing of the fluids included rheological properties, pH and density measurement before hot rolling (BHR) and after hot rolling (AHR) in different pH environments at high pressure and high temperature for long time (up to 4 days).The evaluation of the stability of low density cement utilizing HGS was for their potential to cement shallow casings in gas wells and oil wells in Saudi Arabia. In this study, we present extensive lab work that included rheology measurements, thickening time tests, free water and sedimentation tests, fluid loss test and compressive strength test.Data generated supported the use of low density fluids formulated with HSG in Wasia Formation when applicable. Also, this study supported the use of the cement examined in shallow conditions in gas wells and oil wells. The shallow conditions simulated in the lab tests were 158ºF static temperature and 2500 psi.