Rate transient analysis что это

Обновлено: 05.07.2024

Анализ переходных процессов дебита (RТА = Rate Transient Analysis) производится над откликом дебита скважины на изменение ее забойного давления. Главным преимуществом RТА над PТА является тот факт, что на практике RТА осуществляется на более длительном отрезке времени. В результате анализа RTA определяются те же самые параметры скважины и пласта, что и в PTA:

оценить влияние ствола скважины
оценить скин-фактор
увидеть наличие двойной пористости,
увидеть наличие композитных зон (контрастное изменение гидропроводности по мере удаления от скважины)
определить тип и удаление границы

Главными недостатками этого метода как и в случае с PTA являются

сильная зависимость результатов от интерференции с соседними скважинами, что ограничивает исследование короткими временами
предварительное знание предыстории теста и точных значений дебитов во время теста

и как следствие

неверная оценка гидропроводности
отсутствие возможности выявить факты коммуникации скважины с паразитными пластами
отсутствие возможности оценки геометрии залежи в зоне интерференции с соседями.

На Рис. 1 представлена схема проведения RТА и типичный отклик дебита на тестируемой скважине P1 , в условиях простоя соседних скважин.

Рис. 1. Пример синтетического RТА в условиях простоя окружающих скважин

На этом графике видно, что отклик на тестируемой скважине P1 имеет библиотечный вид, соответствующий режиму частично ограниченной диффузии, сформированной разломами.
На Рис. 2 представлен RTA на той же скважине, но при работающих соседних скважинах.

Рис. 2. Пример синтетического RTA в условиях работающего окружения

На этом графике видно, что отклик на тестируемой скважине P1 сильно искажен на средних и поздних временах влиянием соседних скважин и логарифмическая производная в разные времена времени имеет разные библиотечные типы. По-сути, тест частично испорчен и анализ диффузии должен быть ограничен временем выхода на полку бесконечно-действующего радиального потока (БДРП), в случае, если влияние соседних скважин не искажает отклик на более ранних временах. Рис. 1 показывает, что на скв. P1 это удается сделать, так как влияние соседей сказывается после выхода на полку БДРП. По-сути испорченным оказывается только анализ границ. А вот на скв. P2 влияние соседей оказалось более катастрофичным и испортило отклик на более ранних временах, когда диффузия еще не вышла на режим БДРП. В таком случае по RTA не удается определить ни скин-фактор, ни гидроповодность (см. Табл. 1).

Табл. 1. Сравнение истинных значений и результатов интерпретации RTA

A study of rate transient analysis: Are you making the most of your data?

As engineers, we are currently in an age where we have more data than ever before. However in these times where data is king and we are surrounded by terabytes of data, are we making the best use of what we have available and especially that of flowing pressure data?

The advent of permanent downhole gauges and SCADA systems has made it easier than ever to get reliable well data to your desk, where previously we had to rely on manual gauge reading and the pitfalls that entailed. Now that this data is readily available at your desk, are you willing to make the most of it? This is where Rate Transient Analysis becomes key.

Rate Transient Analysis (RTA), unlike traditional reservoir engineering methods such as Decline Analysis (DCA), incorporates both fluid rates and flowing pressures, where the end goal is to understand the fluid flow in the reservoir. The industry has been doing this with Pressure Transient Analysis (PTA) for many years and RTA is built on exactly the same theory; we are just using the data in a different way.

So why should you use Rate Transient Analysis?

To evaluate reserves with more reliability

Early on in a well’s life, it can sometimes be difficult to deliver an EUR that you believe to be reliable. If the well has only been in decline for a short period of time, decline analysis can produce a number of different forecasts that look equally “good”. This non-uniqueness produces a great deal of uncertainty making it easy to underbook or overbook reserves (see Figure 1). There are also other limitations to decline analysis. For example, when a well is rate restricted, it is not even possible to use decline analysis.

Even if you do have a reasonable DCA forecast, a change in operating conditions means the forecast is no longer valid and a new analysis is required. RTA takes changing operating conditions into account, such as putting a well on pump or compression. Even if the well is producing at a constant rate, you can still generate a forecast without having to go to numerical simulation. RTA allows you to evaluate reserves with a greater amount of confidence due to the physics based nature of the approach.

Figure 1: Which forecast is the most reliable?

Rate Transient Analysis in a way, is like a forensic analysis in that you take a large amount of data and carry out an investigation to help solve the ‘case’. RTA in this sense is a tool for reservoir signal extraction and characterization and allows you to understand the following:

Original fluids in place and reserves
Production optimization potential
Drainage area
Infill potential
Permeability and skin
Stimulation effectiveness
Flow regimes
Pressure support
Well interference

Unlike pressure transient analysis that requires costly shut-ins, Rate Transient Analysis relies on flowing pressures so the well does not need to be shut-in to obtain these results. Generally speaking, Rate Transient Analysis also allows you to see much further into the reservoir than Pressure Transient Analysis because it involves analyzing the entire production history. This is particularly important in low permeability reservoirs or when wells can only be shut-in for short periods of time. For example, when wells are not shut-in long enough to achieve boundary dominated flow, traditional static material balance analysis will lead to incorrect estimates of fluids in place. Alternatively, RTA can be used to conduct a “Flowing Material Balance” on the production data to obtain a better estimate.

Another reason to use RTA is that this data is normally being collected as part of good production practice. With database connections and automated updating of data, these techniques can easily be implemented into the engineer’s work at minimal cost. Once the data is in a comprehensive engineering application for analyzing oil and gas performance and forecasting reserves, like IHS Harmony™, it doesn’t take long to perform an RTA workflow. So within a very short period of time you have an answer you can use to make a decision. There is a very low-cost effort to using RTA, especially when you compare it to the time it takes to do numerical simulation. This is not in any way saying that you should avoid numerical simulation, but rather RTA acts a very good precursor as it can provide information to assist in numerical history matching. This is particularly relevant as it has been noted that there can sometimes be difficulties in tying back production from the field to the model.

In conclusion, with flowing pressure data now so readily available and accessible in programs, Rate Transient Analysis allows engineers to unlock information previously not available, produce more realistic forecasts and aid in numerical simulation.

See more details on the benefits of rate transient analysis in our on-demand webcast, What does pressure have to do with it?

Matthew Bax is an Engineering Sales Manager at IHS Markit.
Posted 25 October 2017

KudoZ™ translation help

Сеть KudoZ - система, позволяющая переводчикам и другим участникам сайта оказывать друг другу помощь в переводе и интерпретации отдельных терминов, словосочетаний и коротких фраз. Calle 14 nro. 622 1/2 entre 44 y 45
La Plata (B1900AND), Buenos Aires
Argentina
+54-221-425-1266 6 Karazina St.
Kharkiv, 61002
Ukraine
+380 57 7281624

Team Coordinators: Natalie
Team Members: Alexey Pylov, Angela Greenfield, esperantisto, svetlana cosquéric, Igor Volosyanoy, VASKON, Sergey Protsenko, Yuliya Masalskaya, Oleksandr Somin, Guzel Rakhimova, Rustam Shafikov, Yana Kalinina, Liudmyla Tavrovska
Просьба принять к сведению, что сайт пока переведен не полностью. Локализация сайта осуществляется поэтапно и первыми переводятся наиболее активные разделы. Если вы обнаружите ошибку в переводе какого-либо раздела сайта, который уже локализован, то сообщите об этом одному из указанных выше координаторов локализации.

Rate Transient Analysis and Numerical Simulation for Under Bubble Point Reservoir

Rate Transient Analysis (RTA) is a modern tool to better understand the capacity of a reservoir. The combination of measured pressure and rate in addition to the relevant analysis structure can lead to estimation of reserves in place. From productivity index and flow equation to flowing material balance model, the total reservoir structure can be observed and the reservoir behavior can be recognized.

Rate transient analysis is science of analyzing production data. In addition to observation of original oil and gas in place, the tool can be used to predict the future behavior of pressure and rate production. The modelling pressure and rates can be used to forecast the reservoir performance and its applicability. RTA can be defined as a modern decline curve analysis method. DCA method is one of the oldest and most often used tools of the petroleum engineers. This is a forecasting technique which predicts by history matching of rate-time data on an appropriate typecurve. What direction to take, what typecurve(s) to choose and where the rate-time data should fit are decided based on basic reservoir engineering concepts and knowledge (Fetkovich 1980; Fetkovich et al. 1987). So DCA is not based on applying a purely empirical equation to be analyzed with statistical approaches which often leads to unrealistic and unreliable forecast and reserve estimate (Fetkovich et al. 1996). RTA also gives convincing estimates of reservoir parameters with available low-frequency (daily, weekly or monthly) production data. Once reservoir characteristics are determined using RTA, a reservoir model is then constructed to forecast future production scenarios (Mishra 2014; Mireault and Dean 2007-2008).

In this case study, an oil well has been observed having reducing trend of GOR. While the pressure having the same declining trend, oil has been stabilized and on some occasions the oil production has a substantial increase. The reservoir pressure is estimated to be 2900psia while the bubble point is 2600psia. The close distance between bubble point and reservoir pressure has led the production falls below the bubble point and release of gas. Now, the question is 'are these gas molecule being produced'? The answer to this questions requires RTA as of below.

Figure 1: Diagnostic Plot

The gas has been released but has led to the increase of oil rate which has been confirmed by the Blasingame type curve. At the same time, gas rate on the surface has been decreased (GOR decrease) and therefore concluded that gas cap is being formed.

Figure 2: Blasingame Type Curve Analysis

The assumption of having the gas cap and the relevant in place volume has been confirmed by flowing material balance model as of below.

Figure 3: Flowing Material Balance and GOR

Based on the gas cap formation the model has been created on FMB and pressure as well as rate has been matched which has led to 22.5MMSTB original oil in place volume.

Figure 4: Flowing Material Balance and Model Match (Estimation of OIIP)

Based on the RTA tank size and the original in place volume, numerical simulation model is created while having the pressure and rates matched. The match has led to prediction of production for this well for the next 10 years.

Figure 5: Numerical Simulation History Match and Prediction

The figure above shows that the gas will be produced eventually, which is leading to the fact that the critical saturation for gas cap will be met.

In conclusion, Harmony Enterprise software has led to proving realization of gas cap which is the second source of energy in the reservoir and can give rise to maintain extra access to proven reserves. All the mentioned process ca has taken time of 3hrs in which is considered very fast processing and simulation task for this field.

Ali Zolalemin is a Reservoir Technical Advisor at IHS Markit.

rate transient analysis

Пояснение:
Здравствуйте Денис,
для более точного перевода, прошу Вас выложить предложение оригинала целиком.

"transient - неустановившееся давление".
"transient - короткий одиночный сейсмический импульс".

Пояснение:
Все ссылки, что я нахожу, указывают на набор методов оценки падения добычи (см. ссылки ниже)

Анализ падения добычи . Арпс, Феткович, Материальный баланс
. well test (pressure transient) and advanced decline (rate transient) analysis .

You will also have access to many other tools and opportunities designed for those who have language-related jobs (or are passionate about them). Participation is free and the site has a strict confidentiality policy.

Читайте также: