1.Text
Palacios Field: A 3-D Case History
In late 1992, Mitchell Energy shot its first 3-D seismic program in the Texas Gulf Coast. The purpose was to unravel a fault pattern consisting of subtle faults — with throws of 30-100 ft — that significantly influence oil and gas production from Palacios Field in Matagorda County. The successful 3-D survey revealed a fault pattern much different from those derived from 2-D data and allowed us to reconstruct the geologic history of the entire area. Although oil and gas development in this area is very mature (the field was discovered in 1937), there are still many things to learn (even for Mitchell, which has been operating here since 1953)…and 3-D is the best teaching tool we havePalacios Field is in the southwestern part of the county. The coastal town of Palacios sits on Tres Palacios Bay just south of the field. Over 230 billion ft3 of gas and 7million bbl oil and condensate, from depths of 7,500 to 15,200ft, have been produced out of this rollover anticlinal feature which is downthrown to a large growth fault that we call, with great originality, the Palacios Fault.图略（此处无法显示）The above figure is a log of the main producing zones, Frio A-G, which are very fine grain sands deposited in shallow water during the Middle Oligocene. The primary zones in this study are the F-l and G sandsMitchell Energy, over the years, purchased more than 200 miles of seismic data over the field. Although most were acquired 20 years ago, reprocessing maintained their usefulness for some time. In 1983, an F-l structure map (Figure 3) was made from these data and well control. This map’s fault pattern had a good fit with all of our data. Also, it supported a simple age-old model in the Texas Gulf Coast; i.e., local faults should run parallel to the main growth fault (the Palacios Fault in this case) and to the coast. The faults should also run parallel to each other and have similar timing. In other words, the model states that the structure should fall within one stress regime that is uniform in time and space. Or as one of our senior vice-presidents said, “Keep it simple, stupid.” And why not? The data fit pretty well. Still, there were some nagging production anomalies that this map could not explainIn 1990, we once again mapped the F-1 sand structure. We added more 2-D data, some of which were recent 40-fold spec data. This map is different from the 1983 map but, in general, it matches the simple structural model that we had in 1983 — parallel faults that are also parallel to the Palacios Fault to the north-west. The 1983 and 1990 maps are only two of many maps made over the years; each had its own fault pattern but all followed the idea of simple parallelismEven though the faults in the field are small (rarely exceeding 100ft of throw), correctly mapping them is critical when determining drainage and predicting reservoir quality. The faults are sealing, and deposition of the sands took place contemporaneously with the faults’ movement. With the 1990 map in hand, we were ready to drill a new development well but we decided that it was in the long-term interest of the field, which we wanted to develop further, to shoot a 3-D seismic survey to help pin down the fault pattern. (Also, the founder of our company, George Mitchell, said we needed to shoot a 3-D survey over the field and we tend to do what George tells us.) The 7.5 mi2 survey was acquired by Tide- lines Geophysical at the end of 19923-D resultsThe red event is the top of the F-l sand. In die initial stages of processing, we loaded a brute stack of the 3-D volume onto a workstation and viewed an early version of this time slice. When we saw it, we were shocked. We immediately realized, from the time slice, that the fault pattern at Palacios was much different than expected. We had predicted that the 3-D survey would lead to some minor changes in fault placement, not a gross realignment of faults. Some faults strike to the northeast and some to the west. Several die out as they extend from the southBased on the 3-D survey, we made a new map of the F-l sand in 1993. There are now three distinct fault systems — designated red, blue, and orange. The blue faults are downthrown to the east and run at a 60°- angle to the Palacios Fault. Also, the structural contours downthrown to the blue faults are parallel to the strike of the faults. Therefore, the fault system created this depositional structure. The F-l sand quality also improves downthrown to these faultsThe red faults are more complicated, but they are all downthrown to the south and run at a 30°-angle to the Palacios Fault. They have similar timing to the blue faults. All but one of the red faults terminate upon intersecting the blue fault system. Their influence on the quality of the F-l sand is less favorableThe third system of faults is the orange system, seen best on the deeper G sand structure map. This fault system is parallel to the Palacios Fault. It is an older fault system that practically died at an angular unconformity that exists between the F and G sands. The unconformity marks the appearance of the Nod. blan. paleomarker and is the top of hard geopressure. The orange faults are critical to trapping gas in the G Sand. The crossline, or strike line shows the three fault systems. The red faults and blue faults are clearly different systems with similar timing. The orange system parallels this seismic line and is difficult to see. It is important to note that all 3-D seismic fault picks were subtle but obvious and exactly matched all fault picks in the wellsGeologic historyWe now recognize that the newly discovered complexity of the Palacios Field fault pattern is due to the history of the Palacios Fault and the deposition of sediment downthrown to it. Some have observed the fault pattern to be that of a radial distribution of faults that might be associated with a diapir. But there is neither salt nor shale diapirism at Palacios Field. The cause of the divergence of the fault systems lies in the deeper Lower Frio sectionThe first significant deposition began with the Lower Frio Anomalina bilat- eralis and Tex. miss, sections. The sand-to-shale ratio is high in the Lower Frio. The shale-prone Middle Frio Discorbis D and Nod. blan. sections were deposited next with the growth rate on the Palacios Fault during Discorbis D time exceeding 100-1. We can demonstrate the presence of only 35 ft of Discorbis D upthrown to the fault, whereas nearly 6000 ft of section lies downthrown to the fault. The growth rate decreased substantially at the top of the Nod. blan. which falls between the F and G sands. The orange faults, parallel to the Palacios Fault, occurred during this time. Stress that caused this faulting was strongly controlled by the Palacios Fault. Also, the growth and movement along the Palacios Fault’s glide plane tilted and displaced basinward the sandy Lower Frio. This section, tilted as much as 40°, was relatively incompressible and acted as a buttress during Upper Frio depositionIt was in Upper Frio time that most of the producing Frio sands were deposited with little growth on the Palacios Fault. The red and blue fault systems were activated as slumps by differential compaction on the flanks of the sand buttress. Without the 3-D survey, we would not have been able to reliably reconstruct the geologic history of the area. So why did we not see this fault pattern with the 2-D data set?
2-D versus 3-DOne reason for the difference between the 2-D maps and the 3-D map is the inadequacy of the 2-D seismic coverage. The 2-D seismic lines are highlighted on the 1990 (before 3-D) map. We interpreted the fault known as “01″ primarily from cuts, some of which were dubious, on several 2-D lines. Green circles highlight key fault intersections that were used to interpret the 01 fault. As a result of the 3-D survey, we discovered the 01 fault cuts were actually the intersections of several different faults with the 2-D seismic lines. We had mistakenly lined up the seismic cuts as those of a single fault. In an effort to keep the fault pat­tern simple on the 2-D maps, this mistake was repeated on other faults. Only with the density of data offered by the 3-D volume could we discern an accurate fault patternAnother 2-D pitfall is the inability to image small faults. One of the 40-fold spec lines we purchased is shown in Figure 13. It is a dip line that runs through the middle of the survey. Its multiplicity is twice that of the highest fold of the 3-D survey, and its trace interval is 82.5ft compared to a bin size of 110 x 110 ft. The original 2-D interpretation is shown. The section in Figure 14 is the 2-D line’s counterpart from the 3-D volume with the 3-D fault interpretation. The horizontal and vertical scales of the two lines are identical. The contrast in the placement and the number of faults is striking. We would never have precisely and accurately interpreted the current fault pattern on the 2-D lineAn obvious question is: “Did the 3-D survey help us find new reserves at Palacios Field?” Answer: Probably not. Maps made before the 3-D survey indicated that fault blocks existed that were undrilled and separated from other wells. Unfortunately, the radial distribution of faults that actually exists showed us that most of the Palacios feature is open to drainage and pressure depletion from most of the wells already drilled there. We now feel that there is some limited potential left there, but nothing commercial at current gas pricesBut, although we did not add reserves as a result of the 3-D survey, we did save moneyAs previously stated, before we shot the 3-D survey, we were fully prepared to drill a well based on the old maps. The 3-D survey kept us from following that course of action. The survey’s cost was about a third of the cost of a development well so savings were approximately $1 million. Moreover, we have learned that small faults are critical in the field and other fields. We are presently working on a nearby 3-D project where small, previously unmapped faults have created compartments, many of which are undrilled. There we hope to make money, not just save itWhen we set out to shoot a 3-D survey over Palacios Field, we simply wanted to firm up some development locations by confirming our fault pattern. Instead we ended up with a much different fault pattern. The reasons are:
1)Inadequate coverage and improper — or lack of — imaging of subtle faults on 2-D seismic lines make it impos­sible to accurately and precisely interpret the correct fault pat­tern2) A simple fault model can be supported by 2-D data, but the complexities of the real world can only be understood with the aid of 3-D seismic dataThe senior vice president who said, “Keep it simple, stupid,” also said to us, “Think like a rock.” For too long, interpreting geophysicists have kept their interpretations too simple, and too wrong, with two-dimensional data. With 3-D data, we can now understand the true structural and stratigraphic nature of our prospects and we can now also formulate significant new ideas about structural and stratigraphic geology in general and on a larger scale than that of our prospects. Indeed, with 3-D data, we are now able to truly think like a rock2.Guidance to Reading
In late 1992, Mitchell Energy shot its first 3-D seismic program in the Texas Gulf Coast. The purpose was to unravel a fault pattern consisting of subtle faults — with throws of 30-100 ft — that significantly influence oil and gas production from Palacios Field in Matagorda County. The successful 3-D survey allowed us to reconstruct the geologic history of the entire area. Although oil and gas development in this area is very mature (the field was discovered in 1937), there are still many things to learn (even for Mitchell, which has been operating here since 1953)，and 3-D is the best teaching tool we have1992年下半年，Mitchell能源公司在得克萨斯海湾沿岸做了首次3D地震测量，其目的是揭示由断距为30-100ft的隐蔽断层所组成的断层组合，这对Matagorda县的Palacios油田的油气生产影响极大。成功的3D地震勘探使我们能重建整个地区的地质发展史。虽然这地区的油气开发相当成熟(该油田发现于1937年)，但仍存在许多事情要研究(即使对1953年就在这里进行勘探的Mitchell公司也是如此)。3D地震测量则是我们最好的研究手段。
3. Words and Expressions
Words
unravel 解开，阐明，弄清楚
fault 断层
throw 距离
survey 调查，测量，勘察
coastal 沿海的
condensate 冷凝物
anticlinal 背斜的
log 详细记录，航海日志
deposite 沉淀，沉积
Oligocene 渐新世（地质时代中古近纪（Paleogene）的最后一个主要分期，大约开始于3400万年前，终于2300万年前，介于始新世（Eocene）与新近纪的中新世（Miocene）之间。）
seismic 地震的
parallel 平行的
regime （某类现象发生时所需的，或者某类现象起主导作用时的）物理条件/环境
nagging 令人心烦的
anomaly 异常，异常现象
drainage 排水系统
reservoir 储层
contemporaneous 同时发生的，同时期的
realignment 重新排列
designate 标明，指定
contour 等值线
terminate 结束，终结
intersect 相交，交叉
unconformity 不整合面
geopressure 地压
sediment 沉淀物
radial 辐射状的，放射式的
diapir 底辟构造
shale 页岩
divergence 分叉，发散
tilt 倾斜
buttress 扶壁，扶垛，支墩，支撑体
flank 侧边，侧翼
dubious 可疑的
discern 看见，发现
pitfall 缺陷
multiplicity 多样性
horizontal 水平的
vertical 垂直的
depletion 消耗，损耗
stratigraphic 地层学的
注：Frio 得克萨斯州南部渐新统弗里奥（Frio）组。Frio 组是一系列相互穿插的海相与非海相的页岩和砂岩。
Phrases and Expressions
consist of 由…组成，构成；
derive from 源自于
run parallel to 与…平行的
40-fold spec data 40次覆盖专用资料
pin down 把…固定住，敲定
a stack of 一堆，大量的
die out 逐渐消失
be associated with 与…有关，相关的
as a result of 由于，根据
in an effort to 为了
runs through 穿过
pressure depletion 压力损耗，压力递减
kept … from doing 使…避免
work on 从事，致力于
set out to do 开始，着手
end up with 以…告终
with the aid of 借助于
in general 总体而言，大体上
on a …scale 在…的规模
4. Language Focus
1. The successful 3-D survey revealed a fault pattern much different from those derived from 2-D data and allowed us to reconstruct the geologic history of the entire area（参考译文：这次成功的3D地震勘探发现了与依据2D地震资料所做的完全不同的断层组合形式，使我们能重建整个地区的地质发展史。）
本句中revealed与allowed是并列谓语。much different from those derived from 2-D data是形容词短语充当a fault pattern的后置定语。在这个结构中derived from 2-D data是过去分词短语充当those的后置定语。
2. With the 1990 map in hand, we were ready to drill a new development well but we decided that it was in the long-term interest of the field, which we wanted to develop further, to shoot a 3-D seismic survey to help pin down the fault pattern（参考译文：我们曾准备用手头上现有的1990年的构造图钻一口新的开发井，但为了油田的长期利益——因为我们想进一步开发它——故我们做了一块3D地震测量以帮助把断层组合敲定下来。）
本句的主干是由but连接的并列句结构。But后面的句子中that…是宾语从句，该从句由it作为不定式to shoot a 3-D seismic survey to help pin down the fault pattern.结构的形式主语。which we wanted to develop further是非限制性定语从句。
3. Unfortunately, the radial distribution of faults that actually exists showed us that most of the Palacios feature is open to drainage and pressure depletion from most of the wells already drilled there（参考译文：不幸的是，实际上存在的放射状分布断层向我们指明，多数Palacios断层特性是与排液系统相通的且从这里许多已钻的井来看，油层压力都已在递减。）
本句中showed是谓语动词，全句主干为主语+谓语+双宾语结构。that actually exists是主语the radial distribution的定语从句。Showed的间接宾语为us，直接宾语是that most of the Palacios feature is open to drainage and pressure depletion from most of the wells already drilled there.从句。从句中already drilled there.是过去分词短语充当the wells的后置定语。
4. We are presently working on a nearby 3-D project where small, previously unmapped faults have created compartments, many of which are undrilled（参考译文：目前，我们已在附近做一块3D勘探，上面有许多小的.以前构造图上没有的断层组成封闭断块，许多断块上还未钻过井。）
本句中We are presently working on a nearby 3-D project是主句；where small, previously unmapped faults have created compartments是地点状语从句；many of which are undrilled是非限制性定语从句。
5. With 3-D data, we can now understand the true structural and stratigraphic nature of our prospects and we can now also formulate significant new ideas about structural and stratigraphic geology in general and on a larger scale than that of our prospects（参考译文：现在用3D地震资料则可以认识到我们所勘探的真实构造和地层特征，并且我们可以更一般地和比我们勘探范围更大地去阐述全新的有关构造地质和地层地质的概念。）
本句主干为and连接的并列句。we can…and we can..5. Reinforced Learning
I. Answer the following questions for a comprehension of the text1. What is the purpose of the 3-D seismic program in the Texas Gulf by Mitchell Energy in late 1992?
2. Why were the researchers shocked when they loaded a stack of the 3-D volume onto a workstation and viewed an early version of this time slice?
3. When were the producing Frio sands deposited on the Palacios Fault.
4. Did the 3-D survey help us find new reserves at Palacios Field? If not, what is the significance of this survey?
5. In the last paragraph, “think like a rock” appears twice. Do they have the same meaning? If not, what’s your interpretation of them?.
II. Multiple choice：choose the correct one from the alternative answers to give the exact meaning of the words1. Police are trying to unravel the mystery of their sudden disappearanceA. answer B. unfasten C. undo D. undertake
2. They designate Mr. yang as director of the laboratoryA. sign B. resign C. appoint D. signal
3. He was just able to discern the road in the darkA. concern B. see C. discover D. uncertain
4. Mankind have been trying every means to maintain the balance of natureA. preserve B. contain C. attain D. captain
5. A week consist of seven daysA. compose of B. is made up of C. make up of D. constitute
6. Thousands of English words derive from LatinA. keep from B. prevent from C. come from D. result from
7. Europe’s foreign ministers met this week in an effort to devise an approach to IranA. effect B. attempt C. affection D. efficiency
8. Streets usually intersect at right anglesA. cross B. interact C. intercept D. interior
9. We interpreted his silence as a refusalA. intended B. understand C. initiated D. innovated
10. Ozone-layer depletion above the Arctic is not as extensive as expected because of unusually warm weatherA. completion B. repetition C. competition D. loss
III. Multiple choice：read the four suggested translations and choose the best answer1. In other words, the model states that the structure should fall within one stress regime that is uniform in time and spaceA. 政体 B. 范围 C. 统治 D. （物理）状态
2. The purpose was to unravel a fault pattern consisting of subtle faultsA. 故障 B. 错误 C. 断层 D. 缺点
3. The above figure is a log of the main producing zones, Frio A-G, which are very fine grain sands deposited in shallow water during the Middle OligoceneA. 圆木 B. 日志 C. 对数 D. 测井
4. Some have observed the fault pattern to be that of a radial distribution of faults that might be associated with a diapirA. 底辟 B. 绝望 C. 维修 D. 灵感
5. But there is neither salt nor shale diapirism at Palacios FieldA. 鲸鱼 B. 形状 C. 页岩 D. 荫凉
IV. Put the following sentences into Chinese1. In late 1992, Mitchell Energy shot its first 3-D seismic program in the Texas Gulf Coast2. Still, there were some nagging production anomalies that this map could not explain3. It was in Upper Frio time that most of the producing Frio sands were deposited with little growth on the Palacios Fault4. Without the 3-D survey, we would not have been able to reliably reconstruct the geologic history of the area5. Only with the density of data offered by the 3-D volume could we discern an accurate fault patternV. Put the following paragraphs into Chinese1. Palacios Field is in the southwestern part of the county. The coastal town of Palacios sits on Tres Palacios Bay just south of the field. Over 230 billion ft3 of gas and 7million bbl oil and condensate, from depths of 7,500 to 15,200ft, have been produced out of this rollover anticlinal feature which is downthrown to a large growth fault that we call, with great originality, the Palacios Fault2. We now recognize that the newly discovered complexity of the Palacios Field fault pattern is due to the history of the Palacios Fault and the deposition of sediment downthrown to it. Some have observed the fault pattern to be that of a radial distribution of faults that might be associated with a diapir. But there is neither salt nor shale diapirism at Palacios Field6. Key to the Exercises
I1. The purpose was to unravel a fault pattern consisting of subtle faults — with throws of 30-100 ft — that significantly influence oil and gas production from Palacios Field in Matagorda County2. Because they realized that the fault pattern at Palacios was much different than expected3. It was in Upper Frio time4. No. But, although we did not add reserves as a result of the 3-D survey, we did save money5. No. The former means to think or act slowly and inflexibly; and the latter means to think calmly and reasonablyII. 1-5 ACBAB 6-10 CBABD
III. 1-5 DCBAC
IV. 1. 1992年下半年，Mitchell能源公司在得克萨斯海湾沿岸做了首次3D地震测量。 2. 可是，仍存在一些令人烦恼的生产异常现象，而这张构造图也解释不了。 3. 在晚Frio期间，大多数产层Frio砂以小的生长率沉积在Palacios断层上。 4. 没有3D勘探，我们不可能这样可靠地重建这个地区的地质发展史。 5. 只有用3D地震所提供的数据密度，我们才能发现一个准确的断层组合。
《石油科技英语》（系列）规划教材编写体例(2)
V1. Palacios油田位于县城西南部，滨海城镇Palacios位于Tres Palacios海湾油田的正南部。已产气2.3 X 1011ft3以上，油和凝析油7 Mbbl，产层埋深为7500~15200 ft，其构造为大的生长断层下降盘的滚动背斜，我们以最初的起源地为名把这个断层称为Palacios断层。
2. 现在我们已认识到Palacios油田断层组合的错综复杂性是由Palacios断层的发育史和在其下降盘沉积物的沉积史所造成的。已观测到的断层组合形式是与刺穿构造有关的放射状分布断层，但在Palacios油田存在的刺穿既不是盐又不是页岩。
7. 参考译文
Palacios油田:一个三维勘探史例
1992年下半年，Mitchell能源公司在得克萨斯海湾沿岸做了首次3D地震测量，其目的是揭示由断距为30-100ft的隐蔽断层所组成的断层组合，这对Matagorda县的Palacios油田的油气生产影响极大。这次成功的3D地震勘探发现了与依据2D地震资料所做的完全不同的断层组合形式，使我们能重建整个地区的地质发展史。虽然这地区的油气开发相当成熟(该油田发现于1937年)，但仍存在许多事情要研究(即使对1953年就在这里进行勘探的Mitchell公司也是如此)。3D地震测量则是我们最好的研究手段。
Palacios油田位于县城西南部，滨海城镇Palacios位于Tres Palacios海湾油田的正南部。已产气2.3 X 1011ft3以上，油和凝析油7 Mbbl，产层埋深为7,500-15,200 ft，其构造为大的生长断层下降盘的滚动背斜，我们以最初的起源地为名把这个断层称为Palacios断层。
上图是主要产层带的测井曲线，Frio A-G是中渐新世期间浅水环境沉积的极细粒砂，本文主要研究F-1和G砂层带。
多年来Mitchell能源公司在油田范围内购买了200多英里的地震资料，虽然大多数资料是在20年前采集的，但对地震资料进行再处理使之在一段时间内还可使用。1983年，利用井控制和这些资料做了F-1砂层的构造图。该图的断层组合与当时资料闭合很好。同时，它还保持着德克萨斯湾海岸简单而古老的模型，即局部断层平行于主生长断层( Palacios断层)和海岸线。这些断层应是平行的并有相似的生成时间。一句话，这个模型认为构造应属于时间、空间上一致的地应力状态。或如我们的一位高级副总裁所说“还是这样简单，笨蛋”。为什么不呢?数据拟合相当好。可是，仍存在一些令人烦恼的生产异常现象，而这张构造图也解释不了。
1990年，我们又做了F-1砂层构造图。这张图用了更多的2D数据，有些还是新近得到的40次覆盖专用资料。该图与1983年的构造图有所不同，但总的来说，它仍保持着1983年得到的简单构造模型即断层组仍平行于西北方向。1983年和1990年的构造图仅仅是多年来所做许多图中的2张；虽然每张图都有它自身的断层组合，但所有的图都遵循着简单平行的思想。
虽然油田中这些断层不大(断距很少超过l00ft)，但是确定排水系统和预测储层质量时，将这些断层正确成图却是至关重要的。这些断层是封闭的，且砂层沉积与断层的活动是同时发生的。我们曾准备用手头上现有的1990年的构造图钻一口新的开发井，但为了油田的长期利益——因为我们想进一步开发它——故我们做了一块3D地震测量以帮助把断层组合敲定下来。(同时，我们公司的创始人George Mitchell说“我们需要对油田做3D地震测量”。我们力图按照George所说的去做。)1992年底，Tide Lines地球物理公司采集了7.5mi2的资料
3D地震勘探结果
红色的同相轴是F-1砂层的顶。在处理的初始阶段，我们把3D初叠数据体加载到一个工作站，以观察时间切片的早期构造形态。当我们看过时间切片后，立刻惊呆了！我们立即从时间切片上认识到Palacios断层的组合与我们预想的差异很大，我们曾预计，3D地震勘探将使断层位置发生某些小的变化，但没有想到会发生断层大的重新组合。有些断层走向西北，有些断层走向西，有些向南延伸时就消失了。
在3D地震勘探的基础上，1993年我们又作了F-1砂层的新构造图。3D地震勘探范围用虚线框在图上标出，其他图上也用虚线框出。在图上存在三种截然不同的断层系统—红色、蓝色和橙色。蓝色断层是东掉断层，并以60度角与Palacios断层相接。蓝色断层下降盘的构造等值线平行于断层的走向，因此断层系统形成这个沉积构造。下降盘的断层改善了F-1砂层的质量。
红色断层是比较复杂的，但它们都是南掉断层，并以30度角与Palacios断层相连。它们与蓝色断层有相似的发育时间。除了一条红色断层外，其余都终止于与蓝色断层系统交会处，对F-1砂层质量的影响不太有利。
第三个断裂系统为桔色断层系统，在更深的G砂层构造图上可以看得更清楚。这个断层系统是平行于Palacios断层。实际上它是消失在位于F和G砂层之间的角度不整合面上的一个老的断层系统。不整合面为Nod.blan.古标志层，它是强地应力的顶。橙色断层对于圈闭G砂层中的气是至关重要的。
在一条横测线(或走向测线)显示出这三种断层系统。红色和蓝色断层是发育时间相似、差异明显的断层系统，而橙色断层因平行于这条地震测线所以很难见到。重要的是要指出，所有3D地震断层拾取是很精细的且很明显，并与井中发现的所有断层吻合得严丝合缝。
地质历史
现在我们已认识到Palacios油田断层组合的错综复杂性是由Palacios断层的发育史和在其下降盘沉积物的沉积史所造成的。已观测到的断层组合形式是与刺穿构造有关的放射状分布断层，但在Palacios油田存在的刺穿既不是盐又不是页岩。造成断层系统发散的原因在于较深的Frio段。
第一次重要的沉积是下Frio Anomalina bilateralis段和Tex.miss.段。在下Frio段中的砂泥岩比率为最高。偏泥相的中Frio Discorbis D和Nod. blun.段接着沉积，而在Discorbis D期间以超过100比1的生长率沉积在Palacios断层上。可以证明Discorbis D层在上升盘仅有35ft，而在下降盘可达近6000ft厚，在F和G砂层之间的Nod. blan.层的顶部生长率大大降低了。平行于Palacios断层的桔色断层是在这段时间产生的，Palacios断层强烈地控制着造成该断层的应力。同时，让Palacios断层的滑动面生长和运动，使砂质下Frio层段向盆地方向倾斜和位移，倾斜度达40°的这个层段，它相对是不可压缩的，成为上Frio沉积期间的支撑体。
在晚Frio期间，大多数产层Frio砂以小的生长率沉积在Palacios断层上，支撑砂体翼部的差异压实作用造成的坍塌使红色和蓝色断层系统十分活跃。没有3D勘探，我们不可能这样可靠地重建这个地区的地质发展史，那么为什么我们在2D地震资料上见不到这种断层组合呢?
2D与3D地震勘探对比
2D和3D地震构造图存在差异的一个原因是2D地震覆盖面不够。将2D地震测线突出标在1990年(3D以前)的构造图上。根据剖面最初解释的断层称为“01”。在几条2D地震剖面上，“01”断层是模糊可疑的。绿色圆圈突出用来解释“01”断层所使用的关键断层交点。根据3D地震勘探的结果，我们发现“01”断层的截点实际上是几种不同断层与2D地震测线的交点。我们错误地把地震测线上的断点给连成一条断层，为了尽力使在2D地震构造图上保持简单的断层组合形式，所以对其余断层也重复这个错误。只有用3D地震所提供的数据密度，我们才能发现一个准确的断层组合。
2D地震的另一个缺陷是不可能对小断层成象。我们购买的一条40次覆盖专用剖面显示于图13。它是穿过测区中部的一条倾向测线，其覆盖次数是3D勘探最高覆盖次数的2倍，道间距为82. 5ft，而相应的 3D面元大小为110ft X 110ft，图中显示出原始的2D解释。图14是根据3D数据体用3D断层解释这条2D测线。两条剖面的水平和垂直比例尺相同，其断层位置和断层条数的差异是惊人的，我们从来没有在2D地震剖面上这样高精度、高准确度地解释出目前的断层组合。
一个明显的问题是“3D地震勘探帮助我们在Palacios油田上找到了新的储量了吗”?回答是没有。在3D测量以前作的构造图指出，存在的断块都是未钻井的且现有的井位都不在上面。不幸的是，实际上存在的放射状分布断层向我们指明，多数Palacios断层特性是与排液系统相通的且从这里许多已钻的井来看，油层压力都已在递减。现在我们感到这里存在的潜力是有限的，对现今的天然气价格是无商业意义的。
虽然3D勘探没有为我们增加油气储量，但却为我们节省了钱。正如我们前面所指出的，在我们实施3D测量之前，我们已经准备好在老构造图的基础上钻一口井，而3D的测量结果使我们避免去钻那口井。因3D勘探费用大约是钻一口开发井费用的1/3。这样可节约经费近100万美元。
进一步，我们已认识到小断层对这个油田和其他油田是至关重要的。目前，我们已在附近做一块3D勘探，上面有许多小的.以前构造图上没有的断层组成封闭断块，许多断块上还未钻过井。在这里我们希望能赚到钱，而不是仅节省钱。
当我们在Palacios油田上开始做3D勘探时，我们只想简单地确认一下断层组合，使一些开发井位置更加牢靠，没想到却以一个完全不同的断层组合而告终。其原因为:
(1)2D地震测线覆盖面不够以及隐蔽断层显示不出或错误成象，使得不可能准确和精细地解释正确的断层组合；
(2)2D地震勘探仅可提供简单的断层组合，而实际地壳的复杂性只能用3D地震数据来理解；
一位高级副总裁曾说“还是这样简单，笨蛋”，又对我们说:“思想还是这样顽固不化”。地球物理解释人员用2D资料才使他们的解释方案太简单，错误百出。现在用3D地震资料则可以认识到我们所勘探的真实构造和地层特征，并且我们可以更一般地和比我们勘探范围更大地去阐述全新的有关构造地质和地层地质的概念。确实，有了3D资料以后，我们现在能够稳如泰山地思考了。
