Autonomous Control of Well Downtime to Optimize Production and Cycling in Sucker Rod Pump Artificially Lifted Wells

For decades sucker rod pump artificially lifted wells have used devices called pump off controllers (POC) to match the pumping unit's runtime to the available reservoir production by idling the well for a set time where variable frequencies drives are not available. In doing this the POC allows the well to enter a set period of downtime when the downhole pump fillage is incomplete to avoid premature failures, and then brings the well back online to operate before production is lost. Although this method has been successful for several years, autonomous control algorithms can be utilized to reduce failures or increase production in cases where the downtime is not already optimized. Optimizing the idle time for a sucker rod pump artificially lifted well involves understanding the amount of time required to fill the near wellbore storage area before generating a fluid column above the pump intake that will begin to hinder inflow from the reservoir into the wellbore. By varying the idle time and observing the impact on production and cycles the program hunts for the optimal idle time. By constantly hunting for the optimal idle time the optimization process can adjust the idle time when operating conditions change. This gives the advantage of always meeting the current well bore and reservoir conditions without having to have a user make these changes and determine what the downtime for the well is. Autonomously modulating the idle time for a well, if done properly will either reduces incomplete fillage pump strokes, in cases where the idle time is too short, or will increase the wells production in cases where the idle time is too long. Overall this will result in the optimization of wells by reducing failures and/or increasing production, generating a huge value to the end user by automating the entire process of downtime optimization.

Optimizing of interpretation build-up with the effect of phase segregation in the lifting tubes

This article explores influence of effect of phase segregation in the listing tubes on results of interpretation the build-up. Phase segregation distorts the actual bottomhole pressure at the start of the well test. Using prior information about the properties of the object: the ratio of the initial and final coefficients of the wellbore storage and skin allow optimize of interpretation the build-up pressure with the effect of phase segregation in the listing tubes

Revisão e Implementação de Soluções Analíticas para a Determinação da Pressão em Poços de Petróleo

<p>A Análise de Testes de Poços é um ramo da Engenharia de Reservatórios no qual<br />empregamos dados de pressão de poço a partir de testes de produção/injeção de fluido em conjunto com modelos físico-matemáticos para caracterizar o sistema poço-reservatório, usando problemas inversos. Nessas situações, aplicamos amplamente soluções analíticas e semianalíticas do modelo físico-matemático que descreve o fluxo. Nesse contexto, o objetivo do presente estudo é 1) realizar uma revisão bibliográfica sobre algumas das soluções analíticas clássicas para determinação da pressão no poço produtor e 2) implementar os códigos numéricos para a criação de uma biblioteca computacional, proporcionando as soluções analíticas voltadas para a determinação da pressão em poços produtores de petróleo. Os sistemas poço-reservatório estudados possuem um poço vertical e levam em consideração os efeitos de condições de contorno, a estocagem na coluna de produção do poço, dano à formação, períodos de fluxo e estática, bem como a presença de fraturas naturais. Obtivemos as soluções analíticas usando a transformada de Laplace e uma inversão numérica, utilizando o algoritmo Stehfest, para calcular a variação de pressão ao longo do tempo.</p><p><br /><strong>Palavras-chave</strong>: Soluções Analíticas, Transformada de Laplace Inversa, Tranformada de Laplace, Algoritmo de Stehfest, Análise de Teste de Poço.</p><p>===================================================================</p><p>Well Testing Analysis is a branch of Reservoir Engineering, in which we<br />employ well pressure data from production tests/fluid injection in conjunction with physical-mathematical models to characterize the well-reservoir system, using inverse problems. In these situations, we widely used analytical and semi-analytical solutions of the physical-mathematical model that describes the flow. In this context, the objective of this work is to 1) carry out a bibliographic review on some of the classic analytical solutions for determining the pressure in the producing well and 2) implement the numerical codes for the creation of a computational library, providing the analytical solutions aimed at determining pressure in oil-producing wells. The well-reservoir systems with a vertical well take into account the boundary effects, wellbore storage, formation damage, drawdown and buildup test analysis, and the presence of natural fractures. We obtain the analytical solutions using the Laplace transform and a numerical inversion, using the Stehfest algorithm, to calculate the pressure variation in the time domain.</p><p><br /><strong>Key words</strong>: Analytical Solutions, Inverve Laplace Transform, Laplace Transform, Stehfest Algorithm, Well Testing Analysis.</p>

New model of reactive transport in a single-well push–pull test with aquitard effect and wellbore storage

The model of single-well push–pull (SWPP) test has been widely used to investigate reactive radial dispersion in remediation or parameter estimation of in situ aquifers. Previous analytical solutions only focused on a completely isolated aquifer for the SWPP test, excluding any influence of aquitards bounding the tested aquifer, and ignored the wellbore storage of the chaser and rest phases in the SWPP test. Such simplification might be questionable in field applications when test durations are relatively long because solute transport in or out of the bounding aquitards is inevitable due to molecular diffusion and cross-formational advective transport. Here, a new SWPP model is developed in an aquifer–aquitard system with wellbore storage, and the analytical solution in the Laplace domain is derived. Four phases of the test are included: the injection phase, the chaser phase, the rest phase and the extraction phase. As the permeability of the aquitard is much smaller than the permeability of the aquifer, the flow is assumed to be perpendicular to the aquitard; thus only vertical dispersive and advective transports are considered for the aquitard. The validity of this treatment is tested against results grounded in numerical simulations. The global sensitivity analysis indicates that the results of the SWPP test are largely sensitive (i.e., influenced by) to the parameters of porosity and radial dispersion of the aquifer, whereas the influence of the aquitard on results could not be ignored. In the injection phase, the larger radial dispersivity of the aquifer could result in the smaller values of breakthrough curves (BTCs), while there are greater BTC values in the chaser and rest phases. In the extraction phase, it could lead to the smaller peak values of BTCs. The new model of this study is a generalization of several previous studies, and it performs better than previous studies ignoring the aquitard effect and wellbore storage for interpreting data of the field SWPP test reported by Yang et al. (2014).