The IDENTIFY study: the investigation and detection of urological neoplasia in patients referred with suspected urinary tract cancer - a multicentre observational study

Objective To evaluate the contemporary prevalence of urinary tract cancer (bladder cancer, upper tract urothelial cancer [UTUC] and renal cancer) in patients referred to secondary care with haematuria, adjusted for established patient risk markers and geographical variation. Patients and Methods This was an international multicentre prospective observational study. We included patients aged ≥16 years, referred to secondary care with suspected urinary tract cancer. Patients with a known or previous urological malignancy were excluded. We estimated the prevalence of bladder cancer, UTUC, renal cancer and prostate cancer; stratified by age, type of haematuria, sex, and smoking. We used a multivariable mixed-effects logistic regression to adjust cancer prevalence for age, type of haematuria, sex, smoking, hospitals, and countries. Results Of the 11 059 patients assessed for eligibility, 10 896 were included from 110 hospitals across 26 countries. The overall adjusted cancer prevalence (n = 2257) was 28.2% (95% confidence interval [CI] 22.3–34.1), bladder cancer (n = 1951) 24.7% (95% CI 19.1–30.2), UTUC (n = 128) 1.14% (95% CI 0.77–1.52), renal cancer (n = 107) 1.05% (95% CI 0.80–1.29), and prostate cancer (n = 124) 1.75% (95% CI 1.32–2.18). The odds ratios for patient risk markers in the model for all cancers were: age 1.04 (95% CI 1.03–1.05; P < 0.001), visible haematuria 3.47 (95% CI 2.90–4.15; P < 0.001), male sex 1.30 (95% CI 1.14–1.50; P < 0.001), and smoking 2.70 (95% CI 2.30–3.18; P < 0.001). Conclusions A better understanding of cancer prevalence across an international population is required to inform clinical guidelines. We are the first to report urinary tract cancer prevalence across an international population in patients referred to secondary care, adjusted for patient risk markers and geographical variation. Bladder cancer was the most prevalent disease. Visible haematuria was the strongest predictor for urinary tract cancer

On the Effect of Mobile Oil Saturation On Fracturing Fluid Leakoff Characteristics In High-permeability Reservoirs

Abstract This paper presents the results of experiments and simulations conducted to investigate the effect of mobile oil saturation on the fracturing fluid leakoff characteristics under dynamic conditions in high permeability reservoir rocks. The fluid leakoff behaviour is examined for samples of varying permeability. In addition, the effectiveness of fluid loss additive in the presence of mobile oil saturation is investigated. A conceptually consistent model to predict the leakoff rate in the presence of mobile oil saturation at the fracture face has been developed. The model is validated using data obtained from dynamic leakoff tests. The results demonstrate that the presence of mobile oil saturation at the fracture face causes the leakoff characteristics to be very different from the tests for which the fracture face is completely saturated with brine. The leakoff characteristics are also affected by the fracture face permeability. Introduction In recent years, increasingly higher permeability formations are being hydraulically fractured (frac-pack) to overcome formation damage and/or prevent sand production problems(1–3). It is usually assumed that during initial stages of frac-pack treatments, a large amount of spurt loss occurs, which contributes to low fluid efficiency and high pumping cost(4). Spurt loss should be controlled in order to reduce the pumping cost and improve the economics of frac-pack treatments. Fluid loss additives are expected to reduce spurt loss by blocking the pore throats of the reservoir rock in the vicinity of the fracture face. In the design of fracturing fluid, the presence of oil in the reservoir which can significantly affect spurt loss and the performance of fluid loss additives, is usually ignored. Very few studies have been published on dynamic fracturing fluid leakoff behaviour in high permeability formation core samples. Further, the core samples in the available studies(4–6) were completely saturated with brine, in contrast to the in situ reservoir samples that have significant oil saturation. The effect of mobile oil saturation in the reservoir on the leakoff characteristics and quality of filter cake has rarely been addressed in the literature. The objective of the present study is to investigate the leakoff behaviour of fracturing fluids in the presence of mobile oil saturation. This objective is accomplished by conducting dynamic filtration experiments on core samples containing mobile oil saturation. A rigorous interpretation of these experiments involving cake build-up and multiphase flow is accomplished by using a mathematical model that incorporates the current understanding of the flow of non-Newtonian fluids, filtration and cake build-up, and multiphase flow in porous media(7). Experimental Setup and Procedures An experimental setup was designed and assembled for studying dynamic leakoff of fracturing fluids in the presence of mobile oil saturation. This setup is similar to the one used in an earlier study(7) except that the core holder is mounted horizontally. Experimental Setup Figure 1 illustrates the schematic of the experimental setup. A detailed description of the setup is presented by Gadiyar et al.(7) The major components of the flow system are: dynamic leakoff core holder, fluid displacement and pumping unit, pressure transducer manifold, and data acquisition system. </jats:sec

The Effect of Fracturing Fluid Leak-Off on the Productivity of High Permeability Oil Reservoirs

Abstract During hydraulic fracturing of permeable reservoirs there is concern that fracturing fluid leak-off may cause a reduction in permeability. One important criterion of a successful fracturing treatment is limited formation damage. This study focused on investigating the alteration of permeability with distance from the fracture face, during fracturing fluid leak-off, and its subsequent recovery during production. Experiments were conducted in a 2-in. diameter and 12-in. long dynamic fluid loss core holder. Ten-in. long Berea sandstone core samples of varying permeabilities were used. Four different types of fracturing fluids were tested. Also, the effect of fluid loss additive on regain permeability was investigated. The movable oil phase in the core sample was either mineral or crude oil. The variation of return permeability with time and distance was determined along the length of the core sample. Effects of shut-in time, fluid loss additive, fracturing fluids, flow rates during flowback, and oil composition on regain permeability of oil reservoirs are presented in this paper. Introduction In recent years, tremendous interest has been developed in hydraulically fracturing high permeability formations(1–3). The objective is to improve production by creating propped fractures which aid in favorably altering the natural flow profiles. In order to optimize productivity, the fractures created should have a very high conductivity and the impairment in formation permeability due to fluid leak-off should be minimal. Fracturing fluids play a major role in the success of a fracturing treatment of high permeability formation. The fracturing fluid is expected to exhibit the following desirable properties:Cause minimum damage to formation permeability due to interaction of filtrate with the matrixGood proppant carrying capacityMinimum fracture conductivity damageFluid loss should be minimal In this paper, the emphasis is on the impact of fracturing fluid leak-off on the regain/return permeability of oil reservoirs. While fracturing a reservoir hydraulically, the fracturing fluid has a tendency to leak-off into the reservoir. The fluid which leaks off into the formation is generally called filtrate. The filtrate consists of polymer and/or particulates which can plug the pore throats, thereby reducing the near fracture face permeability. Usually, the leak-off is enormous in high permeability reservoirs, due to which there is a potential to drastically reduce the near fracture face permeability. This can lead to a reduction in productivity of the reservoir. Few researchers(4–6) have investigated the impairment in formation permeability caused by fracturing fluid leak-off in high permeability reservoirs. Further, all of the past studies were conducted in 100% brine saturated core samples. However, the formations that are hydraulically fractured contain movable oil and/or gas in addition to brine. It has been shown by Gadiyar et al.(7) that the presence of movable oil significantly alters the leak-off behavior of the fracturing fluids. Therefore, one would expect the return permeability and its recovery after leak-off in oil core to be different compared to that observed in 100% brine saturated core. The objective of this study is to investigate the effect of fracturing fluid leak-off on information permeability in the presence of movable oil saturation. </jats:sec

A New Approach for Selecting Sand-Control Technique in Horizontal Openhole Completions

Summary Openhole sand-control technique selection has been a topic of interest since the late 1990s and was discussed most comprehensively in SPE 85504 (Price-Smith et al. 2003), which proposed guidelines for selection between standalone screens (SASs), α/β packing, and shunt-tube packing. Proposed guidelines were based on formation characteristics such as formation strength, particle-size distribution (PSD), mineralogy across the well path; risk factors involved in execution as well as reliability/longevity; and cost considerations. From a PSD standpoint, their guidelines were based on the criteria proposed earlier in SPE 39437 (Tiffin et al. 1998), whereas risk evaluation was based on the technologies available at that time. Since then, significant advancements were made in understanding sand-retention mechanisms and failure modes of SASs, and in technology development to extend the limits of openhole gravel packing. These combined with the field experience in the last decade certainly warrant re-examination of their guidelines, which is the objective of this paper. In this paper, we begin with a critical review of the current sand-control technique-selection methodologies for openhole completions, including the way some of the risk factors are being evaluated to eliminate a given completion technique. On the basis of the technologies developed in the last decade, we propose a new approach for selecting sand-control technique, along with techniques/tools for proper evaluation of the risk factors. The proposed approach significantly extends the application limits of SASs and α/β packing compared with what was proposed in SPE 85504 (Price-Smith et al. 2003).</jats:p