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Abstract There has been discrepancy between the pre-calculated and actual T&D values, because of the dependence of the model’s predictability on assumed inputs. Therefore, to have a reliable model, the users must adjust the model inputs; mainly friction coefficient in order to match the actual T&D. This, however, can mask downhole conditions such as cutting beds, tight holes and sticking tendencies. This paper aims to introduce a machine learning model to predict the continuous profile of the surface drilling torque to detect the operational issues in advance. Actual data of Well-1, starting from the time of drilling a 5-7/8-inch horizontal section until one day prior to the stuck pipe event, was used to train and test a random forest (RF) model with an 80/20 split ratio, to predict the surface drilling torque. The input variables for the model are the drilling surface parameters, namely: flow rate, hook load, rate of penetration, rotary speed, standpipe pressure, and weight-on-bit. The developed model was used to predict the surface drilling torque, which represents the normal trend for the last day leading up to the stuck pipe incident in Well-1. Then the model was integrated with a multivariate metric distance, Mahalanobis, to be used as a classifier to measure how close an actual observation is from the predictive normal trend. Based on a pre-determined threshold, each actual observation was labeled as "NORMAL" or "ANOMAL".
Summary Hydrochloric acid (HCl) is the acid of choice for acidizing operations in most carbonate formations, and is the base acid that is commonly paired with hydrofluoric acid (HF) in most sandstone applications. However, high dissolving power, high corrosion rate, lack of penetration, and sludging tendency coupled with high temperature (HT) can make HCl a poor choice. Alternatively, weaker and less-corrosive chemicals, such as organic acids, can be used instead of HCl to avoid these issues. The objective of this paper is to provide an intensive review on recent advancements, technology, and problems associated with organic acids. The paper focuses on formic, acetic, citric, and lactic acids. This review includes various laboratory evaluation tests and field cases that outline the use of organic acids for formation-damage removal and dissolution. Rotating-disk-apparatus (RDA) results were reviewed to determine the kinetics for acid dissolution of different minerals. Additional results were collected from solubility, corrosion, coreflooding, inductively coupled plasma, X-ray diffraction, and scanning-electron-microscope (SEM) diffraction tests. Because of their retardation performance, organic acids have been used along with mineral acids, mainly a formic/HCl mixture, or as a standalone solution for HT applications. However, the main drawback of these acids is the solubility of reaction-product salts. This challenge has been a limiting factor of using citric acid with calcium-rich formations because of the low solubility of calcium citrate. However, the solubility of the salts associated with formic, acetic, and lactic acid can be increased when these acids are mixed with gluconic acid because of the ability of gluconate ion to chelate calcium-based precipitation. In terms of formation-failure response, organic acids are in lower risk of causing a failure compared with HCl, specifically at deep formation treatments. Organic acids have also been used in other applications. For instance, formic acid is used in HT operations as an intensifier to reduce the corrosion rate caused by HCl. Formic, acetic, and lactic acids can be used to dissolve drilling-mud filter cakes. Citric acid is commonly used as an iron-sequestering agent. This paper shows organic acid advances, limitations, and applications in oil and gas operations, specifically in acidizing jobs. The paper differentiates and closes the gap between various organic acid applications along with providing researchers an intensive guide for present and future research.
Abstract The field study is in northern part of Kuwait targeting heavy oil formation, known to be shallow unconventional oil reservoir. It is heterogeneous shallow sandstone reservoir (500ft TVD) with low maturity oil, has low natural pressure, and poorly consolidated. Mud losses known to be the main risk of horizontal drilling in shallow heavy oil environment and the heterogeneous including continuity of the sand are also challenging for geo-steering team in order to place the well in the optimum position. Seismic is not available, however due to high offset well density a good correlation map has been produced. We are using formation tops from offset wells to delineate the continuity of the sand and trend of the structure dipping, we called it as shooting point method, which is assuming the trend of the structure from one offset well to another nearby offset well. The resistivity contrast will be expected to give us around 9 ft depth of detection (DOD) for our Azitrak resistivity tool based on Picasso plot. We made some scenarios for exiting the reservoir and it showed us some early warning 80ft to 180 ft prior to exit the reservoir. We use Autotrak, Azitrak dan Litotrak formation evaluation and density imaging tool to geo-steer and optimally place the wellbore inside 1B sandstone. The expectation of drilling the lateral was below 1000ft MD due to wellbore stability issue. From the correlation of available offset well it is clearly seen, there are two sand bodies in heavy oil target sand. The thickness is around 30-40 ft TVD and the structure was expected to be flat or a little bit dipping down. The well was landed in the middle of 1B, based on correlation of actual landing point log data to the nearest offset wells. Distance to bed boundary (D2B) showed local conductive layer from bottom since drilling the lateral section, which was not the response of base of 1B sand. So it was recommended to go down in stratigraphy in order to place the trajectory at the bottom part of 1B sand. In order to minimize wellbore stability issue along the lateral section, Bakerhughes recommended to maintain consistent faster ROP (80-100ft/hr) and effective hole cleaning. In the middle of lateral section of well B (1750ft MD) the well trajectory was inverted for the optimum production purposes to total depth (2250ft MD). Total lateral length achieved is 1116ft MD which covers 100% of the lateral length. Shooting point method in defining the rough structure trend from one well to another well was effectively applicative in the field, where current structure after drilling the lateral section is almost flat or slightly dipping down same as predicted before.
Ahmed, Khalid (Kuwait Oil Company) | Abbas, Faisal (Kuwait Oil Company) | Choudhary, Pradeep (Kuwait Oil Company) | Al-Naqi, Ahmad (Kuwait Oil Company) | Ahmad, Abuzar Tanweer (Kuwait Oil Company) | Al-Khamees, Waleed (Kuwait Oil Company)
Abstract Kuwait has an unconsolidated formation with viscous oil at shallow-depth. Drilling and completion of horizontal well at such shallow depth is quite challenging. Industry practice is to use Slant Rig for shallow wells. Drilling experts preferred solution that would not entail Slant Rig for any future interventions and instead suggested using conventional vertical rig to establish feasibility of drilling and completion as a pilot. Lots of pre-drilling studies were carried out which involved Geomechanics Study to understand Stress orientation, pore pressure and sanding risk; Laboratory test of return permeability on core plugs for drilling fluid design and pore-bridging material selection; XRD & SEM analysis for clay mineral identification; Torque and Drag Analysis for predicted performance during drilling and completion and Particle Size Analysis for sand control design with slotted liner. Pre-job coordination meetings, Daily briefings, usage of Rotary Steerable System, Geo-Steering and Mid-course correction of trajectory based on Real Time Data Monitoring resulted in well placement in sweet spot. Well by well, rig days got reduced, lateral lengths increased, tangent sections for pump placement optimised and practically no held up occurred during drilling, casing/liner lowering or completion. This was a World record of drilling horizontal well using vertical rig at such shallow depth. The well completion as verified from Silicon Activation log suggests optimal placement of the slotted liner. This is further vindicated from zero sand and water production, another great achievement for the pilot project. Till date 7 such shallow wells have been drilled with 6 on continuous production for over 2 years in different parts of the field. Successful drilling and completion of these shallow-depth horizontal wells by conventional vertical rig in an efficient and cost-effective manner has confirmed all the pre-drilling assumptions and technological tests for the pilot phase, reaching world record breaking achievement.